On 2020-10-20 15:40, Rob Herring wrote:
On Thu, Sep 24, 2020 at 8:48 AM Rob Herring <robh@xxxxxxxxxx> wrote:
On Cortex-A77 r0p0 and r1p0, a sequence of a non-cacheable or device
load
and a store exclusive or PAR_EL1 read can cause a deadlock.
The workaround requires a DMB SY before and after a PAR_EL1 register
read. In addition, it's possible an interrupt (doing a device read) or
KVM guest exit could be taken between the DMB and PAR read, so we
also need a DMB before returning from interrupt and before returning
to
a guest.
A deadlock is still possible with the workaround as KVM guests must
also
have the workaround. IOW, a malicious guest can deadlock an affected
systems.
This workaround also depends on a firmware counterpart to enable the
h/w
to insert DMB SY after load and store exclusive instructions. See the
errata document SDEN-1152370 v10 [1] for more information.
[1]
https://static.docs.arm.com/101992/0010/Arm_Cortex_A77_MP074_Software_Developer_Errata_Notice_v10.pdf
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: James Morse <james.morse@xxxxxxx>
Cc: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Cc: Marc Zyngier <maz@xxxxxxxxxx>
Cc: Julien Thierry <julien.thierry.kdev@xxxxxxxxx>
Cc: kvmarm@xxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Rob Herring <robh@xxxxxxxxxx>
---
v6:
- Do dmb on kernel_exit rather than disabling interrupts around PAR
read
v5:
- Rebase on v5.9-rc3
- Disable interrupts around PAR reads
- Add DMB on return to guest
v4:
- Move read_sysreg_par out of KVM code to sysreg.h to share
- Also use read_sysreg_par in fault.c and kvm/sys_regs.c
- Use alternative f/w for dmbs around PAR read
- Use cpus_have_final_cap instead of cpus_have_const_cap
- Add note about speculation of PAR read
v3:
- Add dmbs around PAR reads in KVM code
- Clean-up 'work-around' and 'errata'
v2:
- Don't disable KVM, just print warning
---
Documentation/arm64/silicon-errata.rst | 2 ++
arch/arm64/Kconfig | 20 ++++++++++++++++++++
arch/arm64/include/asm/cpucaps.h | 3 ++-
arch/arm64/include/asm/sysreg.h | 9 +++++++++
arch/arm64/kernel/cpu_errata.c | 10 ++++++++++
arch/arm64/kernel/entry.S | 3 +++
arch/arm64/kvm/arm.c | 3 ++-
arch/arm64/kvm/hyp/include/hyp/switch.h | 21 +++++++++++++--------
arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h | 2 +-
arch/arm64/kvm/hyp/nvhe/switch.c | 2 +-
arch/arm64/kvm/hyp/vhe/switch.c | 2 +-
arch/arm64/kvm/sys_regs.c | 2 +-
arch/arm64/mm/fault.c | 2 +-
13 files changed, 66 insertions(+), 15 deletions(-)
Marc, Can I get an ack for KVM on this? Will is waiting for one before
applying.
Here you go:
Acked-by: Marc Zyngier <maz@xxxxxxxxxx>
M.
--
Jazz is not dead. It just smells funny...
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