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Message-ID: <20231114142442.GCZVODKh03BoMFdlmj@fat_crate.local>
Date: Tue, 14 Nov 2023 15:24:42 +0100
From: Borislav Petkov <bp@...en8.de>
To: Michael Roth <michael.roth@....com>
Cc: kvm@...r.kernel.org, linux-coco@...ts.linux.dev,
linux-mm@...ck.org, linux-crypto@...r.kernel.org, x86@...nel.org,
linux-kernel@...r.kernel.org, tglx@...utronix.de, mingo@...hat.com,
jroedel@...e.de, thomas.lendacky@....com, hpa@...or.com,
ardb@...nel.org, pbonzini@...hat.com, seanjc@...gle.com,
vkuznets@...hat.com, jmattson@...gle.com, luto@...nel.org,
dave.hansen@...ux.intel.com, slp@...hat.com, pgonda@...gle.com,
peterz@...radead.org, srinivas.pandruvada@...ux.intel.com,
rientjes@...gle.com, dovmurik@...ux.ibm.com, tobin@....com,
vbabka@...e.cz, kirill@...temov.name, ak@...ux.intel.com,
tony.luck@...el.com, marcorr@...gle.com,
sathyanarayanan.kuppuswamy@...ux.intel.com, alpergun@...gle.com,
jarkko@...nel.org, ashish.kalra@....com, nikunj.dadhania@....com,
pankaj.gupta@....com, liam.merwick@...cle.com,
zhi.a.wang@...el.com, Brijesh Singh <brijesh.singh@....com>
Subject: Re: [PATCH v10 07/50] x86/sev: Add RMP entry lookup helpers
On Mon, Oct 16, 2023 at 08:27:36AM -0500, Michael Roth wrote:
> From: Brijesh Singh <brijesh.singh@....com>
>
> The snp_lookup_page_in_rmptable() can be used by the host to read the RMP
$ git grep snp_lookup_page_in_rmptable
$
Stale commit message. And not very telling. Please rewrite.
> entry for a given page. The RMP entry format is documented in AMD PPR, see
> https://bugzilla.kernel.org/attachment.cgi?id=296015.
<--- Brijesh's SOB comes first here if he's the primary author.
> Co-developed-by: Ashish Kalra <ashish.kalra@....com>
> Signed-off-by: Ashish Kalra <ashish.kalra@....com>
> Signed-off-by: Brijesh Singh <brijesh.singh@....com>
> [mdr: separate 'assigned' indicator from return code]
> Signed-off-by: Michael Roth <michael.roth@....com>
> ---
> arch/x86/include/asm/sev-common.h | 4 +++
> arch/x86/include/asm/sev-host.h | 22 +++++++++++++
> arch/x86/virt/svm/sev.c | 53 +++++++++++++++++++++++++++++++
> 3 files changed, 79 insertions(+)
> create mode 100644 arch/x86/include/asm/sev-host.h
>
> diff --git a/arch/x86/include/asm/sev-common.h b/arch/x86/include/asm/sev-common.h
> index b463fcbd4b90..1e6fb93d8ab0 100644
> --- a/arch/x86/include/asm/sev-common.h
> +++ b/arch/x86/include/asm/sev-common.h
> @@ -173,4 +173,8 @@ struct snp_psc_desc {
> #define GHCB_ERR_INVALID_INPUT 5
> #define GHCB_ERR_INVALID_EVENT 6
>
> +/* RMP page size */
> +#define RMP_PG_SIZE_4K 0
RMP_PG_LEVEL_4K just like the generic ones.
> +#define RMP_TO_X86_PG_LEVEL(level) (((level) == RMP_PG_SIZE_4K) ? PG_LEVEL_4K : PG_LEVEL_2M)
What else is there besides X86 PG level?
IOW, RMP_TO_PG_LEVEL simply.
> +
> #endif
> diff --git a/arch/x86/include/asm/sev-host.h b/arch/x86/include/asm/sev-host.h
Nah, we don't need a third sev header:
arch/x86/include/asm/sev-common.h
arch/x86/include/asm/sev.h
arch/x86/include/asm/sev-host.h
Put it in sev.h pls.
sev-common.h should be merged into sev.h too unless there's a compelling
reason not to which I don't see atm.
> new file mode 100644
> index 000000000000..4c487ce8457f
> --- /dev/null
> +++ b/arch/x86/include/asm/sev-host.h
...
> diff --git a/arch/x86/virt/svm/sev.c b/arch/x86/virt/svm/sev.c
> index 8b9ed72489e4..7d3802605376 100644
> --- a/arch/x86/virt/svm/sev.c
> +++ b/arch/x86/virt/svm/sev.c
> @@ -53,6 +53,9 @@ struct rmpentry {
> */
> #define RMPTABLE_CPU_BOOKKEEPING_SZ 0x4000
>
> +/* Mask to apply to a PFN to get the first PFN of a 2MB page */
> +#define PFN_PMD_MASK (~((1ULL << (PMD_SHIFT - PAGE_SHIFT)) - 1))
GENMASK_ULL
> static struct rmpentry *rmptable_start __ro_after_init;
> static u64 rmptable_max_pfn __ro_after_init;
>
> @@ -237,3 +240,53 @@ static int __init snp_rmptable_init(void)
> * the page(s) used for DMA are hypervisor owned.
> */
> fs_initcall(snp_rmptable_init);
> +
> +static int rmptable_entry(u64 pfn, struct rmpentry *entry)
The signature of this one should be:
static struct rmpentry *get_rmp_entry(u64 pfn)
and the callers should use the IS_ERR* macros to check whether it
returns a valid pointer or a negative value for error.
Ditto for the other two functions here.
> + if (WARN_ON_ONCE(pfn > rmptable_max_pfn))
> + return -EFAULT;
> +
> + *entry = rmptable_start[pfn];
This wants to be called rmptable[] then.
> +
> + return 0;
> +}
> +
> +static int __snp_lookup_rmpentry(u64 pfn, struct rmpentry *entry, int *level)
> +{
> + struct rmpentry large_entry;
> + int ret;
> +
> + if (!cpu_feature_enabled(X86_FEATURE_SEV_SNP))
> + return -ENXIO;
ENODEV or so.
> +
> + ret = rmptable_entry(pfn, entry);
> + if (ret)
> + return ret;
> +
> + /*
> + * Find the authoritative RMP entry for a PFN. This can be either a 4K
> + * RMP entry or a special large RMP entry that is authoritative for a
> + * whole 2M area.
> + */
> + ret = rmptable_entry(pfn & PFN_PMD_MASK, &large_entry);
> + if (ret)
> + return ret;
> +
> + *level = RMP_TO_X86_PG_LEVEL(large_entry.pagesize);
> +
> + return 0;
> +}
> +
> +int snp_lookup_rmpentry(u64 pfn, bool *assigned, int *level)
> +{
> + struct rmpentry e;
> + int ret;
> +
> + ret = __snp_lookup_rmpentry(pfn, &e, level);
> + if (ret)
> + return ret;
> +
> + *assigned = !!e.assigned;
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(snp_lookup_rmpentry);
> --
Thx.
--
Regards/Gruss,
Boris.
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