On Mon, 2022-12-19 at 16:09 +0800, Yuan Yao wrote: > On Fri, Dec 09, 2022 at 12:45:48PM +0800, Robert Hoo wrote: > > ===Feature Introduction=== > > > > Linear-address masking (LAM) [1], modifies the checking that is > > applied to > > *64-bit* linear addresses, allowing software to use of the > > untranslated > > address (upper) bits for metadata. > > As for which upper bits of linear address can be borrowed, LAM has > > 2 modes: > > LAM_48 (bits 62:48, i.e. LAM width of 15) and LAM_57 (bits 62:57, > > i.e. LAM > > width of 6), controlled by these new bits: CR3[62] (LAM_U48), > > CR3[61] > > (LAM_U57), and CR4[28] (LAM_SUP). > > > > * LAM_U48 and LAM_U57 bits controls LAM for user mode address. I.e. > > if > > CR3.LAM_U57 = 1, LAM57 is applied; if CR3.LAM_U48 = 1 and > > CR3.LAM_U57 = 0, > > LAM48 is applied. > > * LAM_SUP bit, combined with paging mode (4-level or 5-level), > > determines > > LAM status for supervisor mode address. I.e. when CR4.LAM_SUP =1, > > 4-level > > paging mode will have LAM48 for supervisor mode address while 5- > > level paging > > will have LAM57. > > > > Note: > > 1. LAM applies to only data address, not to instructions. > > 2. LAM identification of an address as user or supervisor is based > > solely on the > > value of pointer bit 63 and does not, for the purposes of LAM, > > depend on the CPL. > > 3. For user mode address, it is possible that 5-level paging and > > LAM_U48 are both > > set, in this case, the effective usable linear address width is > > 48, i.e. bit > > 56:47 is reserved by LAM. [2] > > It's worth to higlight that vmx exit Guest Linear Address field is > always filled > without the LAM metadata part, it can be used as linear address > directly. OK > I think > this explains reason of no modification on paging_tmpl.h for shadow > paging. > > > > > > > ===LAM KVM Design=== > > > > Pass CR4.LAM_SUP under guest control. > > > > Under EPT mode, CR3 is fully under guest control, guest LAM is thus > > transparent to > > KVM. Nothing more need to do. > > > > For Shadow paging (EPT = off), KVM need to handle guest CR3.LAM_U48 > > and CR3.LAM_U57 > > toggles. > > > > Patch 1 -- This patch can be mostly independent from LAM enabling. > > It just renames > > CR4 reserved bits for better understanding, esp. for > > beginners. > > > > Patch 2, 9 -- Common part for both EPT and Shadow Paging modes > > enabling. > > > > Patch 3 ~ 8 -- For Shadow Paging mode LAM enabling. > > > > [1] ISE Chap10 https://cdrdv2.intel.com/v1/dl/getContent/671368 > > (Section 10.6 VMX interaction) > > [2] Thus currently, Kernel enabling patch only enables LAM57 mode. > > https://lore.kernel.org/lkml/20220815041803.17954-1-kirill.shutemov@xxxxxxxxxxxxxxx/ > > > > --- > > Changelog > > v2 --> v3: > > As LAM Kernel patches are in tip tree now, rebase to it. > > https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git/ > > > > v1 --> v2: > > 1. Fixes i386-allyesconfig build error on get_pgd(), where > > CR3_HIGH_RSVD_MASK isn't applicable. > > (Reported-by: kernel test robot <lkp@xxxxxxxxx>) > > 2. In kvm_set_cr3(), be conservative on skip tlb flush when only > > LAM bits > > toggles. (Kirill) > > > > Robert Hoo (9): > > KVM: x86: Rename cr4_reserved/rsvd_* variables to be more > > readable > > KVM: x86: Add CR4.LAM_SUP in guest owned bits > > KVM: x86: MMU: Rename get_cr3() --> get_pgd() and clear high bits > > for > > pgd > > KVM: x86: MMU: Commets update > > KVM: x86: MMU: Integrate LAM bits when build guest CR3 > > KVM: x86: Untag LAM bits when applicable > > KVM: x86: When judging setting CR3 valid or not, consider LAM > > bits > > KVM: x86: When guest set CR3, handle LAM bits semantics > > KVM: x86: LAM: Expose LAM CPUID to user space VMM > > > > arch/x86/include/asm/kvm_host.h | 7 ++-- > > arch/x86/include/asm/processor-flags.h | 1 + > > arch/x86/kvm/cpuid.c | 6 +-- > > arch/x86/kvm/kvm_cache_regs.h | 3 +- > > arch/x86/kvm/mmu.h | 5 +++ > > arch/x86/kvm/mmu/mmu.c | 18 ++++++--- > > arch/x86/kvm/vmx/vmx.c | 8 +++- > > arch/x86/kvm/x86.c | 51 ++++++++++++++++++++ > > ------ > > arch/x86/kvm/x86.h | 43 +++++++++++++++++++++- > > 9 files changed, 115 insertions(+), 27 deletions(-) > > > > > > base-commit: a5dadcb601b4954c60494d797b4dd1e03a4b1ebe > > -- > > 2.31.1 > >
