On Mon, Jun 22, 2015 at 06:41:32PM +0800, Zhichao Huang wrote:
> Implement switching of the debug registers. While the number
> of registers is massive, CPUs usually don't implement them all
> (A15 has 6 breakpoints and 4 watchpoints, which gives us a total
> of 22 registers "only").
>
> Notice that, for ARMv7, if the CONFIG_HAVE_HW_BREAKPOINT is set in
> the guest, debug is always actively in use (ARM_DSCR_MDBGEN set).
>
> We have to do the save/restore dance in this case, because the host
> and the guest might use their respective debug registers at any moment.
this sounds expensive, and I suggested an alternative approach in the
previsou patch. In any case, measuring the impact on this on hardware
would be a great idea...
>
> If the CONFIG_HAVE_HW_BREAKPOINT is not set, and if no one flagged
> the debug registers as dirty, we only save/resotre DBGDSCR.
restore
>
> Signed-off-by: Zhichao Huang <zhichao.huang@xxxxxxxxxx>
> ---
> arch/arm/kvm/interrupts.S | 16 +++
> arch/arm/kvm/interrupts_head.S | 249 ++++++++++++++++++++++++++++++++++++++++-
> 2 files changed, 263 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm/kvm/interrupts.S b/arch/arm/kvm/interrupts.S
> index 79caf79..d626275 100644
> --- a/arch/arm/kvm/interrupts.S
> +++ b/arch/arm/kvm/interrupts.S
> @@ -116,6 +116,12 @@ ENTRY(__kvm_vcpu_run)
> read_cp15_state store_to_vcpu = 0
> write_cp15_state read_from_vcpu = 1
>
> + @ Store hardware CP14 state and load guest state
> + compute_debug_state 1f
> + bl __save_host_debug_regs
> + bl __restore_guest_debug_regs
> +
> +1:
> @ If the host kernel has not been configured with VFPv3 support,
> @ then it is safer if we deny guests from using it as well.
> #ifdef CONFIG_VFPv3
> @@ -201,6 +207,16 @@ after_vfp_restore:
> mrc p15, 0, r2, c0, c0, 5
> mcr p15, 4, r2, c0, c0, 5
>
> + @ Store guest CP14 state and restore host state
> + skip_debug_state 1f
> + bl __save_guest_debug_regs
> + bl __restore_host_debug_regs
> + /* Clear the dirty flag for the next run, as all the state has
> + * already been saved. Note that we nuke the whole 32bit word.
> + * If we ever add more flags, we'll have to be more careful...
> + */
> + clear_debug_dirty_bit
> +1:
> @ Store guest CP15 state and restore host state
> read_cp15_state store_to_vcpu = 1
> write_cp15_state read_from_vcpu = 0
> diff --git a/arch/arm/kvm/interrupts_head.S b/arch/arm/kvm/interrupts_head.S
> index 5662c39..ed406be 100644
> --- a/arch/arm/kvm/interrupts_head.S
> +++ b/arch/arm/kvm/interrupts_head.S
> @@ -7,6 +7,7 @@
> #define VCPU_USR_SP (VCPU_USR_REG(13))
> #define VCPU_USR_LR (VCPU_USR_REG(14))
> #define CP15_OFFSET(_cp15_reg_idx) (VCPU_CP15 + (_cp15_reg_idx * 4))
> +#define CP14_OFFSET(_cp14_reg_idx) (VCPU_CP14 + ((_cp14_reg_idx) * 4))
>
> /*
> * Many of these macros need to access the VCPU structure, which is always
> @@ -168,8 +169,7 @@ vcpu .req r0 @ vcpu pointer always in r0
> * Clobbers *all* registers.
> */
> .macro restore_guest_regs
> - /* reset DBGDSCR to disable debug mode */
> - mov r2, #0
> + ldr r2, [vcpu, #CP14_OFFSET(cp14_DBGDSCRext)]
> mcr p14, 0, r2, c0, c2, 2
>
> restore_guest_regs_mode svc, #VCPU_SVC_REGS
> @@ -250,6 +250,10 @@ vcpu .req r0 @ vcpu pointer always in r0
> save_guest_regs_mode abt, #VCPU_ABT_REGS
> save_guest_regs_mode und, #VCPU_UND_REGS
> save_guest_regs_mode irq, #VCPU_IRQ_REGS
> +
> + /* DBGDSCR reg */
> + mrc p14, 0, r2, c0, c1, 0
> + str r2, [vcpu, #CP14_OFFSET(cp14_DBGDSCRext)]
> .endm
>
> /* Reads cp15 registers from hardware and stores them in memory
> @@ -449,6 +453,231 @@ vcpu .req r0 @ vcpu pointer always in r0
> str r5, [vcpu, #VCPU_DEBUG_FLAGS]
> .endm
>
> +/* Assume r11/r12 in used, clobbers r2-r10 */
> +.macro cp14_read_and_push Op2 skip_num
> + cmp \skip_num, #8
> + // if (skip_num >= 8) then skip c8-c15 directly
> + bge 1f
> + adr r2, 9998f
> + add r2, r2, \skip_num, lsl #2
> + bx r2
> +1:
> + adr r2, 9999f
> + sub r3, \skip_num, #8
> + add r2, r2, r3, lsl #2
> + bx r2
> +9998:
> + mrc p14, 0, r10, c0, c15, \Op2
> + mrc p14, 0, r9, c0, c14, \Op2
> + mrc p14, 0, r8, c0, c13, \Op2
> + mrc p14, 0, r7, c0, c12, \Op2
> + mrc p14, 0, r6, c0, c11, \Op2
> + mrc p14, 0, r5, c0, c10, \Op2
> + mrc p14, 0, r4, c0, c9, \Op2
> + mrc p14, 0, r3, c0, c8, \Op2
> + push {r3-r10}
you probably don't want to do more stores to memory than required
> +9999:
> + mrc p14, 0, r10, c0, c7, \Op2
> + mrc p14, 0, r9, c0, c6, \Op2
> + mrc p14, 0, r8, c0, c5, \Op2
> + mrc p14, 0, r7, c0, c4, \Op2
> + mrc p14, 0, r6, c0, c3, \Op2
> + mrc p14, 0, r5, c0, c2, \Op2
> + mrc p14, 0, r4, c0, c1, \Op2
> + mrc p14, 0, r3, c0, c0, \Op2
> + push {r3-r10}
same
> +.endm
> +
> +/* Assume r11/r12 in used, clobbers r2-r10 */
> +.macro cp14_pop_and_write Op2 skip_num
> + cmp \skip_num, #8
> + // if (skip_num >= 8) then skip c8-c15 directly
> + bge 1f
> + adr r2, 9998f
> + add r2, r2, \skip_num, lsl #2
> + pop {r3-r10}
you probably don't want to do more loads from memory than required
> + bx r2
> +1:
> + adr r2, 9999f
> + sub r3, \skip_num, #8
> + add r2, r2, r3, lsl #2
> + pop {r3-r10}
same
> + bx r2
> +
> +9998:
> + mcr p14, 0, r10, c0, c15, \Op2
> + mcr p14, 0, r9, c0, c14, \Op2
> + mcr p14, 0, r8, c0, c13, \Op2
> + mcr p14, 0, r7, c0, c12, \Op2
> + mcr p14, 0, r6, c0, c11, \Op2
> + mcr p14, 0, r5, c0, c10, \Op2
> + mcr p14, 0, r4, c0, c9, \Op2
> + mcr p14, 0, r3, c0, c8, \Op2
> +
> + pop {r3-r10}
> +9999:
> + mcr p14, 0, r10, c0, c7, \Op2
> + mcr p14, 0, r9, c0, c6, \Op2
> + mcr p14, 0, r8, c0, c5, \Op2
> + mcr p14, 0, r7, c0, c4, \Op2
> + mcr p14, 0, r6, c0, c3, \Op2
> + mcr p14, 0, r5, c0, c2, \Op2
> + mcr p14, 0, r4, c0, c1, \Op2
> + mcr p14, 0, r3, c0, c0, \Op2
> +.endm
> +
> +/* Assume r11/r12 in used, clobbers r2-r3 */
> +.macro cp14_read_and_str Op2 cp14_reg0 skip_num
> + adr r3, 1f
> + add r3, r3, \skip_num, lsl #3
> + bx r3
> +1:
> + mrc p14, 0, r2, c0, c15, \Op2
> + str r2, [vcpu, #CP14_OFFSET(\cp14_reg0+15)]
> + mrc p14, 0, r2, c0, c14, \Op2
> + str r2, [vcpu, #CP14_OFFSET(\cp14_reg0+14)]
> + mrc p14, 0, r2, c0, c13, \Op2
> + str r2, [vcpu, #CP14_OFFSET(\cp14_reg0+13)]
> + mrc p14, 0, r2, c0, c12, \Op2
> + str r2, [vcpu, #CP14_OFFSET(\cp14_reg0+12)]
> + mrc p14, 0, r2, c0, c11, \Op2
> + str r2, [vcpu, #CP14_OFFSET(\cp14_reg0+11)]
> + mrc p14, 0, r2, c0, c10, \Op2
> + str r2, [vcpu, #CP14_OFFSET(\cp14_reg0+10)]
> + mrc p14, 0, r2, c0, c9, \Op2
> + str r2, [vcpu, #CP14_OFFSET(\cp14_reg0+9)]
> + mrc p14, 0, r2, c0, c8, \Op2
> + str r2, [vcpu, #CP14_OFFSET(\cp14_reg0+8)]
> + mrc p14, 0, r2, c0, c7, \Op2
> + str r2, [vcpu, #CP14_OFFSET(\cp14_reg0+7)]
> + mrc p14, 0, r2, c0, c6, \Op2
> + str r2, [vcpu, #CP14_OFFSET(\cp14_reg0+6)]
> + mrc p14, 0, r2, c0, c5, \Op2
> + str r2, [vcpu, #CP14_OFFSET(\cp14_reg0+5)]
> + mrc p14, 0, r2, c0, c4, \Op2
> + str r2, [vcpu, #CP14_OFFSET(\cp14_reg0+4)]
> + mrc p14, 0, r2, c0, c3, \Op2
> + str r2, [vcpu, #CP14_OFFSET(\cp14_reg0+3)]
> + mrc p14, 0, r2, c0, c2, \Op2
> + str r2, [vcpu, #CP14_OFFSET(\cp14_reg0+2)]
> + mrc p14, 0, r2, c0, c1, \Op2
> + str r2, [vcpu, #CP14_OFFSET(\cp14_reg0+1)]
> + mrc p14, 0, r2, c0, c0, \Op2
> + str r2, [vcpu, #CP14_OFFSET(\cp14_reg0)]
> +.endm
> +
> +/* Assume r11/r12 in used, clobbers r2-r3 */
> +.macro cp14_ldr_and_write Op2 cp14_reg0 skip_num
> + adr r3, 1f
> + add r3, r3, \skip_num, lsl #3
> + bx r3
> +1:
> + ldr r2, [vcpu, #CP14_OFFSET(\cp14_reg0+15)]
> + mcr p14, 0, r2, c0, c15, \Op2
> + ldr r2, [vcpu, #CP14_OFFSET(\cp14_reg0+14)]
> + mcr p14, 0, r2, c0, c14, \Op2
> + ldr r2, [vcpu, #CP14_OFFSET(\cp14_reg0+13)]
> + mcr p14, 0, r2, c0, c13, \Op2
> + ldr r2, [vcpu, #CP14_OFFSET(\cp14_reg0+12)]
> + mcr p14, 0, r2, c0, c12, \Op2
> + ldr r2, [vcpu, #CP14_OFFSET(\cp14_reg0+11)]
> + mcr p14, 0, r2, c0, c11, \Op2
> + ldr r2, [vcpu, #CP14_OFFSET(\cp14_reg0+10)]
> + mcr p14, 0, r2, c0, c10, \Op2
> + ldr r2, [vcpu, #CP14_OFFSET(\cp14_reg0+9)]
> + mcr p14, 0, r2, c0, c9, \Op2
> + ldr r2, [vcpu, #CP14_OFFSET(\cp14_reg0+8)]
> + mcr p14, 0, r2, c0, c8, \Op2
> + ldr r2, [vcpu, #CP14_OFFSET(\cp14_reg0+7)]
> + mcr p14, 0, r2, c0, c7, \Op2
> + ldr r2, [vcpu, #CP14_OFFSET(\cp14_reg0+6)]
> + mcr p14, 0, r2, c0, c6, \Op2
> + ldr r2, [vcpu, #CP14_OFFSET(\cp14_reg0+5)]
> + mcr p14, 0, r2, c0, c5, \Op2
> + ldr r2, [vcpu, #CP14_OFFSET(\cp14_reg0+4)]
> + mcr p14, 0, r2, c0, c4, \Op2
> + ldr r2, [vcpu, #CP14_OFFSET(\cp14_reg0+3)]
> + mcr p14, 0, r2, c0, c3, \Op2
> + ldr r2, [vcpu, #CP14_OFFSET(\cp14_reg0+2)]
> + mcr p14, 0, r2, c0, c2, \Op2
> + ldr r2, [vcpu, #CP14_OFFSET(\cp14_reg0+1)]
> + mcr p14, 0, r2, c0, c1, \Op2
> + ldr r2, [vcpu, #CP14_OFFSET(\cp14_reg0)]
> + mcr p14, 0, r2, c0, c0, \Op2
> +.endm
can you not find some way of unifying cp14_pop_and_write with
cp14_ldr_and_write and cp14_read_and_push with cp14_read_and_str ?
Probably having two separate structs for the VFP state on the vcpu struct
for both the guest and the host state is one possible way of doing so.
> +
> +/* Get extract number of BRPs and WRPs. Saved in r11/r12 */
> +.macro read_hw_dbg_num
> + mrc p14, 0, r2, c0, c0, 0
> + ubfx r11, r2, #24, #4
> + add r11, r11, #1 // Extract BRPs
> + ubfx r12, r2, #28, #4
> + add r12, r12, #1 // Extract WRPs
> + mov r2, #16
> + sub r11, r2, r11 // How many BPs to skip
> + sub r12, r2, r12 // How many WPs to skip
> +.endm
> +
> +/* Reads cp14 registers from hardware.
You have a lot of multi-line comments in these patches which don't start
with a separate '/*' line, as dictated by the Linux kernel coding style.
So far, I've ignored this, but please fix all these throughout the
series when you respin.
> + * Writes cp14 registers in-order to the stack.
> + *
> + * Assumes vcpu pointer in vcpu reg
> + *
> + * Clobbers r2-r12
> + */
> +.macro save_host_debug_regs
> + read_hw_dbg_num
> + cp14_read_and_push #4, r11 @ DBGBVR
> + cp14_read_and_push #5, r11 @ DBGBCR
> + cp14_read_and_push #6, r12 @ DBGWVR
> + cp14_read_and_push #7, r12 @ DBGWCR
> +.endm
> +
> +/* Reads cp14 registers from hardware.
> + * Writes cp14 registers in-order to the VCPU struct pointed to by vcpup.
> + *
> + * Assumes vcpu pointer in vcpu reg
> + *
> + * Clobbers r2-r12
> + */
> +.macro save_guest_debug_regs
> + read_hw_dbg_num
> + cp14_read_and_str #4, cp14_DBGBVR0, r11
why do you need the has before the op2 field?
> + cp14_read_and_str #5, cp14_DBGBCR0, r11
> + cp14_read_and_str #6, cp14_DBGWVR0, r12
> + cp14_read_and_str #7, cp14_DBGWCR0, r12
> +.endm
> +
> +/* Reads cp14 registers in-order from the stack.
> + * Writes cp14 registers to hardware.
> + *
> + * Assumes vcpu pointer in vcpu reg
> + *
> + * Clobbers r2-r12
> + */
> +.macro restore_host_debug_regs
> + read_hw_dbg_num
> + cp14_pop_and_write #4, r11 @ DBGBVR
> + cp14_pop_and_write #5, r11 @ DBGBCR
> + cp14_pop_and_write #6, r12 @ DBGWVR
> + cp14_pop_and_write #7, r12 @ DBGWCR
> +.endm
> +
> +/* Reads cp14 registers in-order from the VCPU struct pointed to by vcpup
> + * Writes cp14 registers to hardware.
> + *
> + * Assumes vcpu pointer in vcpu reg
> + *
> + * Clobbers r2-r12
> + */
> +.macro restore_guest_debug_regs
> + read_hw_dbg_num
> + cp14_ldr_and_write #4, cp14_DBGBVR0, r11
> + cp14_ldr_and_write #5, cp14_DBGBCR0, r11
> + cp14_ldr_and_write #6, cp14_DBGWVR0, r12
> + cp14_ldr_and_write #7, cp14_DBGWCR0, r12
> +.endm
> +
> /*
> * Save the VGIC CPU state into memory
> *
> @@ -684,3 +913,19 @@ ARM_BE8(rev r6, r6 )
> .macro load_vcpu
> mrc p15, 4, vcpu, c13, c0, 2 @ HTPIDR
> .endm
> +
> +__save_host_debug_regs:
> + save_host_debug_regs
> + bx lr
> +
> +__save_guest_debug_regs:
> + save_guest_debug_regs
> + bx lr
> +
> +__restore_host_debug_regs:
> + restore_host_debug_regs
> + bx lr
> +
> +__restore_guest_debug_regs:
> + restore_guest_debug_regs
> + bx lr
> --
> 1.7.12.4
>
Thanks,
-Christoffer
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