From 30579c8baa5b4bd986420a984dad2940f1ff65d3 Mon Sep 17 00:00:00 2001 From: "Borislav Petkov (AMD)" Date: Thu, 30 Nov 2023 14:26:01 +0100 Subject: x86/sev: Do the C-bit verification only on the BSP There's no need to do it on every AP. The C-bit value read on the BSP and also verified there, is used everywhere from now on. No functional changes - just a bit faster booting APs. Signed-off-by: Borislav Petkov (AMD) Acked-by: Tom Lendacky Link: https://lore.kernel.org/r/20231130132601.10317-1-bp@alien8.de --- arch/x86/kernel/head_64.S | 31 ++++++++++++++++++++++--------- 1 file changed, 22 insertions(+), 9 deletions(-) diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S index 086a2c3aaaa0..d1dc39af6771 100644 --- a/arch/x86/kernel/head_64.S +++ b/arch/x86/kernel/head_64.S @@ -114,6 +114,28 @@ SYM_CODE_START_NOALIGN(startup_64) /* Form the CR3 value being sure to include the CR3 modifier */ addq $(early_top_pgt - __START_KERNEL_map), %rax + +#ifdef CONFIG_AMD_MEM_ENCRYPT + mov %rax, %rdi + mov %rax, %r14 + + addq phys_base(%rip), %rdi + + /* + * For SEV guests: Verify that the C-bit is correct. A malicious + * hypervisor could lie about the C-bit position to perform a ROP + * attack on the guest by writing to the unencrypted stack and wait for + * the next RET instruction. + */ + call sev_verify_cbit + + /* + * Restore CR3 value without the phys_base which will be added + * below, before writing %cr3. + */ + mov %r14, %rax +#endif + jmp 1f SYM_CODE_END(startup_64) @@ -192,15 +214,6 @@ SYM_INNER_LABEL(secondary_startup_64_no_verify, SYM_L_GLOBAL) /* Setup early boot stage 4-/5-level pagetables. */ addq phys_base(%rip), %rax - /* - * For SEV guests: Verify that the C-bit is correct. A malicious - * hypervisor could lie about the C-bit position to perform a ROP - * attack on the guest by writing to the unencrypted stack and wait for - * the next RET instruction. - */ - movq %rax, %rdi - call sev_verify_cbit - /* * Switch to new page-table * -- cgit From d642ef7111014805f2e21e9cddb0c0a93ae1313d Mon Sep 17 00:00:00 2001 From: Uwe Kleine-König Date: Tue, 26 Dec 2023 14:28:03 +0100 Subject: virt: sev-guest: Convert to platform remove callback returning void MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The .remove() callback for a platform driver returns an int which makes many driver authors wrongly assume it's possible to do error handling by returning an error code. However the value returned is ignored (apart from emitting a warning) and this typically results in resource leaks. To improve here there is a quest to make the remove callback return void. In the first step of this quest all drivers are converted to .remove_new(), which already returns void. Eventually after all drivers are converted, .remove_new() will be renamed to .remove(). Trivially convert this driver from always returning zero in the remove callback to the void returning variant. Signed-off-by: Uwe Kleine-König Signed-off-by: Borislav Petkov (AMD) Acked-by: Tom Lendacky Link: https://lore.kernel.org/r/52826a50250304ab0af14c594009f7b901c2cd31.1703596577.git.u.kleine-koenig@pengutronix.de --- drivers/virt/coco/sev-guest/sev-guest.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/drivers/virt/coco/sev-guest/sev-guest.c b/drivers/virt/coco/sev-guest/sev-guest.c index bc564adcf499..87f241825bc3 100644 --- a/drivers/virt/coco/sev-guest/sev-guest.c +++ b/drivers/virt/coco/sev-guest/sev-guest.c @@ -994,7 +994,7 @@ e_unmap: return ret; } -static int __exit sev_guest_remove(struct platform_device *pdev) +static void __exit sev_guest_remove(struct platform_device *pdev) { struct snp_guest_dev *snp_dev = platform_get_drvdata(pdev); @@ -1003,8 +1003,6 @@ static int __exit sev_guest_remove(struct platform_device *pdev) free_shared_pages(snp_dev->request, sizeof(struct snp_guest_msg)); deinit_crypto(snp_dev->crypto); misc_deregister(&snp_dev->misc); - - return 0; } /* @@ -1013,7 +1011,7 @@ static int __exit sev_guest_remove(struct platform_device *pdev) * with the SEV-SNP support, it is named "sev-guest". */ static struct platform_driver sev_guest_driver = { - .remove = __exit_p(sev_guest_remove), + .remove_new = __exit_p(sev_guest_remove), .driver = { .name = "sev-guest", }, -- cgit