Re: [PATCH 08/10] KVM/X86: Use kvm_vcpu_map in emulator_cmpxchg_emulated

Raslan, KarimAllah
2018-02-22T02:56:12Z

On Wed, 2018-02-21 at 18:47 +0100, KarimAllah Ahmed wrote:
> ... since using kvm_vcpu_gpa_to_page() and kmap() will only work for guest
> memory that has a "struct page".
>
> Signed-off-by: KarimAllah Ahmed <karahmed@amazon.de>
> ---
> arch/x86/kvm/x86.c | 13 ++++++-------
> 1 file changed, 6 insertions(+), 7 deletions(-)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 37f5df9..197a395 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -5013,9 +5013,9 @@ static int emulator_cmpxchg_emulated(struct x86_emulate_ctxt *ctxt,
> unsigned int bytes,
> struct x86_exception *exception)
> {
> + struct kvm_host_map map;

"map" here needs to be memset to '0'. Will fix in v2

> struct kvm_vcpu *vcpu = emul_to_vcpu(ctxt);
> gpa_t gpa;
> - struct page *page;
> char *kaddr;
> bool exchanged;
>
> @@ -5032,12 +5032,11 @@ static int emulator_cmpxchg_emulated(struct x86_emulate_ctxt *ctxt,
> if (((gpa + bytes - 1) & PAGE_MASK) != (gpa & PAGE_MASK))
> goto emul_write;
>
> - page = kvm_vcpu_gfn_to_page(vcpu, gpa >> PAGE_SHIFT);
> - if (is_error_page(page))
> + if (!kvm_vcpu_map(vcpu, gpa_to_gfn(gpa), &map))
> goto emul_write;
>
> - kaddr = kmap_atomic(page);
> - kaddr += offset_in_page(gpa);
> + kaddr = map.kaddr + offset_in_page(gpa);
> +
> switch (bytes) {
> case 1:
> exchanged = CMPXCHG_TYPE(u8, kaddr, old, new);
> @@ -5054,8 +5053,8 @@ static int emulator_cmpxchg_emulated(struct x86_emulate_ctxt *ctxt,
> default:
> BUG();
> }
> - kunmap_atomic(kaddr);
> - kvm_release_page_dirty(page);
> +
> + kvm_vcpu_unmap(&map);
>
> if (!exchanged)
> return X86EMUL_CMPXCHG_FAILED;
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