Re: [PATCH v2] KVM: SVM: Mark SEV launch secret pages as dirty.

[Brijesh Singh]

On 8/7/20 7:37 PM, Cfir Cohen wrote:
> The LAUNCH_SECRET command performs encryption of the
> launch secret memory contents. Mark pinned pages as
> dirty, before unpinning them.
> This matches the logic in sev_launch_update_data().
>
> Signed-off-by: Cfir Cohen 
> ---
> Changelog since v1:
>  - Updated commit message.
>
>  arch/x86/kvm/svm/sev.c | 15 ++-
>  1 file changed, 14 insertions(+), 1 deletion(-)


Reviewed-by: Brijesh Singh 


>
> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> index 5573a97f1520..37c47d26b9f7 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -850,7 +850,7 @@ static int sev_launch_secret(struct kvm *kvm, struct 
> kvm_sev_cmd *argp)
>   struct kvm_sev_launch_secret params;
>   struct page **pages;
>   void *blob, *hdr;
> - unsigned long n;
> + unsigned long n, i;
>   int ret, offset;
>  
>   if (!sev_guest(kvm))
> @@ -863,6 +863,14 @@ static int sev_launch_secret(struct kvm *kvm, struct 
> kvm_sev_cmd *argp)
>   if (!pages)
>   return -ENOMEM;
>  
> + /*
> +  * The LAUNCH_SECRET command will perform in-place encryption of the
> +  * memory content (i.e it will write the same memory region with C=1).
> +  * It's possible that the cache may contain the data with C=0, i.e.,
> +  * unencrypted so invalidate it first.
> +  */
> + sev_clflush_pages(pages, n);
> +
>   /*
>* The secret must be copied into contiguous memory region, lets verify
>* that userspace memory pages are contiguous before we issue command.
> @@ -908,6 +916,11 @@ static int sev_launch_secret(struct kvm *kvm, struct 
> kvm_sev_cmd *argp)
>  e_free:
>   kfree(data);
>  e_unpin_memory:
> + /* content of memory is updated, mark pages dirty */
> + for (i = 0; i < n; i++) {
> + set_page_dirty_lock(pages[i]);
> + mark_page_accessed(pages[i]);
> + }
>   sev_unpin_memory(kvm, pages, n);
>   return ret;
>  }

[PATCH v2] KVM: SVM: Mark SEV launch secret pages as dirty.

[Cfir Cohen]

The LAUNCH_SECRET command performs encryption of the
launch secret memory contents. Mark pinned pages as
dirty, before unpinning them.
This matches the logic in sev_launch_update_data().

Signed-off-by: Cfir Cohen 
---
Changelog since v1:
 - Updated commit message.

 arch/x86/kvm/svm/sev.c | 15 ++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 5573a97f1520..37c47d26b9f7 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -850,7 +850,7 @@ static int sev_launch_secret(struct kvm *kvm, struct 
kvm_sev_cmd *argp)
struct kvm_sev_launch_secret params;
struct page **pages;
void *blob, *hdr;
-   unsigned long n;
+   unsigned long n, i;
int ret, offset;
 
if (!sev_guest(kvm))
@@ -863,6 +863,14 @@ static int sev_launch_secret(struct kvm *kvm, struct 
kvm_sev_cmd *argp)
if (!pages)
return -ENOMEM;
 
+   /*
+* The LAUNCH_SECRET command will perform in-place encryption of the
+* memory content (i.e it will write the same memory region with C=1).
+* It's possible that the cache may contain the data with C=0, i.e.,
+* unencrypted so invalidate it first.
+*/
+   sev_clflush_pages(pages, n);
+
/*
 * The secret must be copied into contiguous memory region, lets verify
 * that userspace memory pages are contiguous before we issue command.
@@ -908,6 +916,11 @@ static int sev_launch_secret(struct kvm *kvm, struct 
kvm_sev_cmd *argp)
 e_free:
kfree(data);
 e_unpin_memory:
+   /* content of memory is updated, mark pages dirty */
+   for (i = 0; i < n; i++) {
+   set_page_dirty_lock(pages[i]);
+   mark_page_accessed(pages[i]);
+   }
sev_unpin_memory(kvm, pages, n);
return ret;
 }
-- 
2.28.0.236.gb10cc79966-goog