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authorBrijesh Singh <brijesh.singh@amd.com>2018-09-14 08:45:58 -0500
committerThomas Gleixner <tglx@linutronix.de>2018-09-15 20:48:45 +0200
commitb3f0907c71e006e12fde74ea9a745b6096b6f90f (patch)
treedb20afaf037c1228abafd1e2b6718f68698f0d35 /arch/x86/kernel/head64.c
parent27c5a778dfe23d1de8d9ebfbc6a54595a79ac709 (diff)
downloadlinux-b3f0907c71e006e12fde74ea9a745b6096b6f90f.tar.bz2
x86/mm: Add .bss..decrypted section to hold shared variables
kvmclock defines few static variables which are shared with the hypervisor during the kvmclock initialization. When SEV is active, memory is encrypted with a guest-specific key, and if the guest OS wants to share the memory region with the hypervisor then it must clear the C-bit before sharing it. Currently, we use kernel_physical_mapping_init() to split large pages before clearing the C-bit on shared pages. But it fails when called from the kvmclock initialization (mainly because the memblock allocator is not ready that early during boot). Add a __bss_decrypted section attribute which can be used when defining such shared variable. The so-defined variables will be placed in the .bss..decrypted section. This section will be mapped with C=0 early during boot. The .bss..decrypted section has a big chunk of memory that may be unused when memory encryption is not active, free it when memory encryption is not active. Suggested-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Brijesh Singh <brijesh.singh@amd.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Tom Lendacky <thomas.lendacky@amd.com> Cc: Borislav Petkov <bp@suse.de> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: Sean Christopherson <sean.j.christopherson@intel.com> Cc: Radim Krčmář<rkrcmar@redhat.com> Cc: kvm@vger.kernel.org Link: https://lkml.kernel.org/r/1536932759-12905-2-git-send-email-brijesh.singh@amd.com
Diffstat (limited to 'arch/x86/kernel/head64.c')
-rw-r--r--arch/x86/kernel/head64.c16
1 files changed, 16 insertions, 0 deletions
diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
index 8047379e575a..c16af27eb23f 100644
--- a/arch/x86/kernel/head64.c
+++ b/arch/x86/kernel/head64.c
@@ -112,6 +112,7 @@ static bool __head check_la57_support(unsigned long physaddr)
unsigned long __head __startup_64(unsigned long physaddr,
struct boot_params *bp)
{
+ unsigned long vaddr, vaddr_end;
unsigned long load_delta, *p;
unsigned long pgtable_flags;
pgdval_t *pgd;
@@ -235,6 +236,21 @@ unsigned long __head __startup_64(unsigned long physaddr,
sme_encrypt_kernel(bp);
/*
+ * Clear the memory encryption mask from the .bss..decrypted section.
+ * The bss section will be memset to zero later in the initialization so
+ * there is no need to zero it after changing the memory encryption
+ * attribute.
+ */
+ if (mem_encrypt_active()) {
+ vaddr = (unsigned long)__start_bss_decrypted;
+ vaddr_end = (unsigned long)__end_bss_decrypted;
+ for (; vaddr < vaddr_end; vaddr += PMD_SIZE) {
+ i = pmd_index(vaddr);
+ pmd[i] -= sme_get_me_mask();
+ }
+ }
+
+ /*
* Return the SME encryption mask (if SME is active) to be used as a
* modifier for the initial pgdir entry programmed into CR3.
*/