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    SubjectRe: [PATCH v3 09/10] KVM: MMU: fix MTRR update
    Hi Xiao,
    On Wed, May 13, 2015 at 02:42:27PM +0800, Xiao Guangrong wrote:
    >Currently, whenever guest MTRR registers are changed
    >kvm_mmu_reset_context is called to switch to the new root shadow page
    >table, however, it's useless since:
    >1) the cache type is not cached into shadow page's attribute so that
    > the original root shadow page will be reused

    kvm_mmu_reset_context
    kvm_mmu_unload
    mmu_free_roots

    The original root shadow page will be freed in mmu_free_roots, where I
    miss?

    Another question maybe not related to this patch:

    If kvm_mmu_reset_context is just called to destroy the original root
    shadow page and all the sptes will remain valid?

    Regards,
    Wanpeng Li

    >
    >2) the cache type is set on the last spte, that means we should sync
    > the last sptes when MTRR is changed
    >
    >This patch fixs this issue by drop all the spte in the gfn range which
    >is being updated by MTRR
    >
    >Signed-off-by: Xiao Guangrong <guangrong.xiao@linux.intel.com>
    >---
    > arch/x86/kvm/x86.c | 59 +++++++++++++++++++++++++++++++++++++++++++++++++++++-
    > 1 file changed, 58 insertions(+), 1 deletion(-)
    >
    >diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
    >index cde5d61..bbe184f 100644
    >--- a/arch/x86/kvm/x86.c
    >+++ b/arch/x86/kvm/x86.c
    >@@ -1852,6 +1852,63 @@ bool kvm_mtrr_valid(struct kvm_vcpu *vcpu, u32 msr, u64 data)
    > }
    > EXPORT_SYMBOL_GPL(kvm_mtrr_valid);
    >
    >+static void update_mtrr(struct kvm_vcpu *vcpu, u32 msr)
    >+{
    >+ struct mtrr_state_type *mtrr_state = &vcpu->arch.mtrr_state;
    >+ unsigned char mtrr_enabled = mtrr_state->enabled;
    >+ gfn_t start, end, mask;
    >+ int index;
    >+ bool is_fixed = true;
    >+
    >+ if (msr == MSR_IA32_CR_PAT || !tdp_enabled ||
    >+ !kvm_arch_has_noncoherent_dma(vcpu->kvm))
    >+ return;
    >+
    >+ if (!(mtrr_enabled & 0x2) && msr != MSR_MTRRdefType)
    >+ return;
    >+
    >+ switch (msr) {
    >+ case MSR_MTRRfix64K_00000:
    >+ start = 0x0;
    >+ end = 0x80000;
    >+ break;
    >+ case MSR_MTRRfix16K_80000:
    >+ start = 0x80000;
    >+ end = 0xa0000;
    >+ break;
    >+ case MSR_MTRRfix16K_A0000:
    >+ start = 0xa0000;
    >+ end = 0xc0000;
    >+ break;
    >+ case MSR_MTRRfix4K_C0000 ... MSR_MTRRfix4K_F8000:
    >+ index = msr - MSR_MTRRfix4K_C0000;
    >+ start = 0xc0000 + index * (32 << 10);
    >+ end = start + (32 << 10);
    >+ break;
    >+ case MSR_MTRRdefType:
    >+ is_fixed = false;
    >+ start = 0x0;
    >+ end = ~0ULL;
    >+ break;
    >+ default:
    >+ /* variable range MTRRs. */
    >+ is_fixed = false;
    >+ index = (msr - 0x200) / 2;
    >+ start = (((u64)mtrr_state->var_ranges[index].base_hi) << 32) +
    >+ (mtrr_state->var_ranges[index].base_lo & PAGE_MASK);
    >+ mask = (((u64)mtrr_state->var_ranges[index].mask_hi) << 32) +
    >+ (mtrr_state->var_ranges[index].mask_lo & PAGE_MASK);
    >+ mask |= ~0ULL << cpuid_maxphyaddr(vcpu);
    >+
    >+ end = ((start & mask) | ~mask) + 1;
    >+ }
    >+
    >+ if (is_fixed && !(mtrr_enabled & 0x1))
    >+ return;
    >+
    >+ kvm_zap_gfn_range(vcpu->kvm, gpa_to_gfn(start), gpa_to_gfn(end));
    >+}
    >+
    > static int set_msr_mtrr(struct kvm_vcpu *vcpu, u32 msr, u64 data)
    > {
    > u64 *p = (u64 *)&vcpu->arch.mtrr_state.fixed_ranges;
    >@@ -1885,7 +1942,7 @@ static int set_msr_mtrr(struct kvm_vcpu *vcpu, u32 msr, u64 data)
    > *pt = data;
    > }
    >
    >- kvm_mmu_reset_context(vcpu);
    >+ update_mtrr(vcpu, msr);
    > return 0;
    > }
    >
    >--
    >2.1.0
    >
    >--
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