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Message-ID: <57a6e04d-b95d-83b1-aa0b-fb2f7174e47d@amd.com>
Date: Wed, 16 Oct 2024 16:55:18 +0530
From: "Nikunj A. Dadhania" <nikunj@....com>
To: Tom Lendacky <thomas.lendacky@....com>, linux-kernel@...r.kernel.org,
x86@...nel.org
Cc: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>,
Michael Roth <michael.roth@....com>, Ashish Kalra <ashish.kalra@....com>
Subject: Re: [sos-linux-ext-patches] [PATCH v3 5/8] x86/sev: Map only the RMP
table entries instead of the full RMP range
On 9/30/2024 8:52 PM, Tom Lendacky wrote:
> In preparation for support of a segmented RMP table, map only the RMP
s/support of/supporting/
> table entries. The RMP bookkeeping area is only ever accessed when
> first enabling SNP and does not need to remain mapped. To accomplish
> this, split the initialization of the RMP bookkeeping area and the
> initialization of the RMP entry area. The RMP bookkeeping area will be
> mapped only while it is being initialized.
>
> Signed-off-by: Tom Lendacky <thomas.lendacky@....com>
Reviewed-by: Nikunj A Dadhania <nikunj@....com>
> ---
> arch/x86/virt/svm/sev.c | 36 +++++++++++++++++++++++++++++++-----
> 1 file changed, 31 insertions(+), 5 deletions(-)
>
> diff --git a/arch/x86/virt/svm/sev.c b/arch/x86/virt/svm/sev.c
> index 31d1510ae119..81e21d833cf0 100644
> --- a/arch/x86/virt/svm/sev.c
> +++ b/arch/x86/virt/svm/sev.c
> @@ -168,6 +168,23 @@ void __init snp_fixup_e820_tables(void)
> __snp_fixup_e820_tables(probed_rmp_base + probed_rmp_size);
> }
>
> +static bool __init init_rmptable_bookkeeping(void)
> +{
> + void *bk;
> +
> + bk = memremap(probed_rmp_base, RMPTABLE_CPU_BOOKKEEPING_SZ, MEMREMAP_WB);
> + if (!bk) {
> + pr_err("Failed to map RMP bookkeeping area\n");
> + return false;
> + }
> +
> + memset(bk, 0, RMPTABLE_CPU_BOOKKEEPING_SZ);
> +
> + memunmap(bk);
> +
> + return true;
> +}
> +
> /*
> * Do the necessary preparations which are verified by the firmware as
> * described in the SNP_INIT_EX firmware command description in the SNP
> @@ -205,12 +222,17 @@ static int __init snp_rmptable_init(void)
> goto nosnp;
> }
>
> - rmptable_start = memremap(probed_rmp_base, probed_rmp_size, MEMREMAP_WB);
> + /* Map only the RMP entries */
> + rmptable_start = memremap(probed_rmp_base + RMPTABLE_CPU_BOOKKEEPING_SZ,
> + probed_rmp_size - RMPTABLE_CPU_BOOKKEEPING_SZ,
> + MEMREMAP_WB);
> if (!rmptable_start) {
> pr_err("Failed to map RMP table\n");
> goto nosnp;
> }
>
> + rmptable_size = probed_rmp_size - RMPTABLE_CPU_BOOKKEEPING_SZ;
> +
> /*
> * Check if SEV-SNP is already enabled, this can happen in case of
> * kexec boot.
> @@ -219,7 +241,14 @@ static int __init snp_rmptable_init(void)
> if (val & MSR_AMD64_SYSCFG_SNP_EN)
> goto skip_enable;
>
> - memset(rmptable_start, 0, probed_rmp_size);
> + /* Zero out the RMP bookkeeping area */
> + if (!init_rmptable_bookkeeping()) {
> + memunmap(rmptable_start);
> + goto nosnp;
> + }
> +
> + /* Zero out the RMP entries */
> + memset(rmptable_start, 0, rmptable_size);
>
> /* Flush the caches to ensure that data is written before SNP is enabled. */
> wbinvd_on_all_cpus();
> @@ -230,9 +259,6 @@ static int __init snp_rmptable_init(void)
> on_each_cpu(snp_enable, NULL, 1);
>
> skip_enable:
> - rmptable_start += RMPTABLE_CPU_BOOKKEEPING_SZ;
> - rmptable_size = probed_rmp_size - RMPTABLE_CPU_BOOKKEEPING_SZ;
> -
> rmptable = (struct rmpentry_raw *)rmptable_start;
> rmptable_max_pfn = rmptable_size / sizeof(struct rmpentry_raw) - 1;
>
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