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Message-ID: <YU2fQMgw+PIBzSE4@zn.tnic>
Date: Fri, 24 Sep 2021 11:49:52 +0200
From: Borislav Petkov <bp@...en8.de>
To: Brijesh Singh <brijesh.singh@....com>
Cc: x86@...nel.org, linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
linux-coco@...ts.linux.dev, linux-mm@...ck.org,
linux-crypto@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Joerg Roedel <jroedel@...e.de>,
Tom Lendacky <thomas.lendacky@....com>,
"H. Peter Anvin" <hpa@...or.com>, Ard Biesheuvel <ardb@...nel.org>,
Paolo Bonzini <pbonzini@...hat.com>,
Sean Christopherson <seanjc@...gle.com>,
Vitaly Kuznetsov <vkuznets@...hat.com>,
Wanpeng Li <wanpengli@...cent.com>,
Jim Mattson <jmattson@...gle.com>,
Andy Lutomirski <luto@...nel.org>,
Dave Hansen <dave.hansen@...ux.intel.com>,
Sergio Lopez <slp@...hat.com>, Peter Gonda <pgonda@...gle.com>,
Peter Zijlstra <peterz@...radead.org>,
Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
David Rientjes <rientjes@...gle.com>,
Dov Murik <dovmurik@...ux.ibm.com>,
Tobin Feldman-Fitzthum <tobin@....com>,
Michael Roth <michael.roth@....com>,
Vlastimil Babka <vbabka@...e.cz>,
"Kirill A . Shutemov" <kirill@...temov.name>,
Andi Kleen <ak@...ux.intel.com>, tony.luck@...el.com,
marcorr@...gle.com, sathyanarayanan.kuppuswamy@...ux.intel.com
Subject: Re: [PATCH Part2 v5 04/45] x86/sev: Add RMP entry lookup helpers
On Fri, Aug 20, 2021 at 10:58:37AM -0500, Brijesh Singh wrote:
> +struct __packed rmpentry {
> + union {
> + struct {
> + u64 assigned : 1,
> + pagesize : 1,
> + immutable : 1,
> + rsvd1 : 9,
> + gpa : 39,
> + asid : 10,
> + vmsa : 1,
> + validated : 1,
> + rsvd2 : 1;
> + } info;
> + u64 low;
> + };
> + u64 high;
> +};
__packed goes at the end of the struct definition.
> +
> +#define rmpentry_assigned(x) ((x)->info.assigned)
> +#define rmpentry_pagesize(x) ((x)->info.pagesize)
Inline functions pls so that you can get typechecking too.
>
> #define RMPADJUST_VMSA_PAGE_BIT BIT(16)
>
> diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
> index 7936c8139c74..f383d2a89263 100644
> --- a/arch/x86/kernel/sev.c
> +++ b/arch/x86/kernel/sev.c
> @@ -54,6 +54,8 @@
> * bookkeeping, the range need to be added during the RMP entry lookup.
> */
> #define RMPTABLE_CPU_BOOKKEEPING_SZ 0x4000
> +#define RMPENTRY_SHIFT 8
> +#define rmptable_page_offset(x) (RMPTABLE_CPU_BOOKKEEPING_SZ + (((unsigned long)x) >> RMPENTRY_SHIFT))
>
> /* For early boot hypervisor communication in SEV-ES enabled guests */
> static struct ghcb boot_ghcb_page __bss_decrypted __aligned(PAGE_SIZE);
> @@ -2376,3 +2378,44 @@ static int __init snp_rmptable_init(void)
> * available after subsys_initcall().
> */
> fs_initcall(snp_rmptable_init);
> +
> +static struct rmpentry *__snp_lookup_rmpentry(u64 pfn, int *level)
> +{
> + unsigned long vaddr, paddr = pfn << PAGE_SHIFT;
> + struct rmpentry *entry, *large_entry;
> +
> + if (!pfn_valid(pfn))
> + return ERR_PTR(-EINVAL);
> +
> + if (!cpu_feature_enabled(X86_FEATURE_SEV_SNP))
> + return ERR_PTR(-ENXIO);
I think that check should happen first.
> +
> + vaddr = rmptable_start + rmptable_page_offset(paddr);
> + if (unlikely(vaddr > rmptable_end))
> + return ERR_PTR(-ENXIO);
Maybe the above -E should be -ENOENT instead so that you have unique
error types for each check to facilitate debugging.
> +
> + entry = (struct rmpentry *)vaddr;
> +
> + /* Read a large RMP entry to get the correct page level used in RMP entry. */
That comment needs rewriting.
> + vaddr = rmptable_start + rmptable_page_offset(paddr & PMD_MASK);
> + large_entry = (struct rmpentry *)vaddr;
> + *level = RMP_TO_X86_PG_LEVEL(rmpentry_pagesize(large_entry));
> +
> + return entry;
> +}
> +
> +/*
> + * Return 1 if the RMP entry is assigned, 0 if it exists but is not assigned,
> + * and -errno if there is no corresponding RMP entry.
> + */
kernel-doc format since it is being exported.
> +int snp_lookup_rmpentry(u64 pfn, int *level)
> +{
> + struct rmpentry *e;
> +
> + e = __snp_lookup_rmpentry(pfn, level);
> + if (IS_ERR(e))
> + return PTR_ERR(e);
> +
> + return !!rmpentry_assigned(e);
> +}
> +EXPORT_SYMBOL_GPL(snp_lookup_rmpentry);
This export is for kvm, I presume?
> diff --git a/include/linux/sev.h b/include/linux/sev.h
> new file mode 100644
> index 000000000000..1a68842789e1
> --- /dev/null
> +++ b/include/linux/sev.h
> @@ -0,0 +1,30 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * AMD Secure Encrypted Virtualization
> + *
> + * Author: Brijesh Singh <brijesh.singh@....com>
> + */
> +
> +#ifndef __LINUX_SEV_H
> +#define __LINUX_SEV_H
> +
> +/* RMUPDATE detected 4K page and 2MB page overlap. */
> +#define RMPUPDATE_FAIL_OVERLAP 7
> +
> +#ifdef CONFIG_AMD_MEM_ENCRYPT
> +int snp_lookup_rmpentry(u64 pfn, int *level);
> +int psmash(u64 pfn);
> +int rmp_make_private(u64 pfn, u64 gpa, enum pg_level level, int asid, bool immutable);
> +int rmp_make_shared(u64 pfn, enum pg_level level);
> +#else
> +static inline int snp_lookup_rmpentry(u64 pfn, int *level) { return 0; }
> +static inline int psmash(u64 pfn) { return -ENXIO; }
> +static inline int rmp_make_private(u64 pfn, u64 gpa, enum pg_level level, int asid,
> + bool immutable)
> +{
> + return -ENODEV;
> +}
> +static inline int rmp_make_shared(u64 pfn, enum pg_level level) { return -ENODEV; }
> +
> +#endif /* CONFIG_AMD_MEM_ENCRYPT */
> +#endif /* __LINUX_SEV_H */
> --
What is going to use this linux/ namespace header?
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
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