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    SubjectRe: [PATCH v8 12/40] x86/sev: Add helper for validating pages in early enc attribute changes
    On 2021-12-10 09:43:04 -0600, Brijesh Singh wrote:
    > The early_set_memory_{encrypt,decrypt}() are used for changing the

    s/encrypt,decrypt/encrypted,decrypted/

    > page from decrypted (shared) to encrypted (private) and vice versa.
    > When SEV-SNP is active, the page state transition needs to go through
    > additional steps.
    >
    > If the page is transitioned from shared to private, then perform the
    > following after the encryption attribute is set in the page table:
    >
    > 1. Issue the page state change VMGEXIT to add the page as a private
    > in the RMP table.
    > 2. Validate the page after its successfully added in the RMP table.
    >
    > To maintain the security guarantees, if the page is transitioned from
    > private to shared, then perform the following before clearing the
    > encryption attribute from the page table.
    >
    > 1. Invalidate the page.
    > 2. Issue the page state change VMGEXIT to make the page shared in the
    > RMP table.
    >
    > The early_set_memory_{encrypt,decrypt} can be called before the GHCB

    s/encrypt,decrypt/encrypted,decrypted/

    > is setup, use the SNP page state MSR protocol VMGEXIT defined in the GHCB
    > specification to request the page state change in the RMP table.
    >
    > While at it, add a helper snp_prep_memory() that can be used outside
    > the sev specific files to change the page state for a specified memory
    > range.
    >
    > Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>

    And with a few other nits below:

    Reviewed-by: Venu Busireddy <venu.busireddy@oracle.com>

    > diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
    > +
    > + /*
    > + * Ask the hypervisor to mark the memory pages as private in the RMP
    > + * table.
    > + */

    Indentation is off. While at it, you may want to collapse it into a one
    line comment.

    > + early_set_page_state(paddr, npages, SNP_PAGE_STATE_PRIVATE);
    > +
    > + /* Validate the memory pages after they've been added in the RMP table. */
    > + pvalidate_pages(vaddr, npages, 1);
    > +}
    > +
    > +void __init early_snp_set_memory_shared(unsigned long vaddr, unsigned long paddr,
    > + unsigned int npages)
    > +{
    > + if (!cc_platform_has(CC_ATTR_SEV_SNP))
    > + return;
    > +
    > + /*
    > + * Invalidate the memory pages before they are marked shared in the
    > + * RMP table.
    > + */

    Collapse into one line?

    > + pvalidate_pages(vaddr, npages, 0);
    > +
    > + /* Ask hypervisor to mark the memory pages shared in the RMP table. */

    Indentation is off.

    > + /*
    > + * ON SNP, the page state in the RMP table must happen
    > + * before the page table updates.
    > + */
    > + early_snp_set_memory_shared((unsigned long)__va(pa), pa, 1);

    I know "1" implies "true", but to emphasize that the argument is
    actually a boolean, could you please change the "1" to "true?"

    > + }
    > +
    > /* Change the page encryption mask. */
    > new_pte = pfn_pte(pfn, new_prot);
    > set_pte_atomic(kpte, new_pte);
    > +
    > + /*
    > + * If page is set encrypted in the page table, then update the RMP table to
    > + * add this page as private.
    > + */
    > + if (enc)
    > + early_snp_set_memory_private((unsigned long)__va(pa), pa, 1);

    Here too, could you please change the "1" to "true?"

    Venu

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