From d92b54570d24d017d2630e314b525ed792f5aa6c Mon Sep 17 00:00:00 2001 From: Arvind Sankar Date: Tue, 24 Dec 2019 14:29:07 +0100 Subject: [PATCH 1/3] efi/earlycon: Fix write-combine mapping on x86 On x86, until PAT is initialized, WC translates into UC-. Since we calculate and store pgprot_writecombine(PAGE_KERNEL) when earlycon is initialized, this means we actually use UC- mappings instead of WC mappings, which makes scrolling very slow. Instead store a boolean flag to indicate whether we want to use writeback or write-combine mappings, and recalculate the actual pgprot_t we need on every mapping. Once PAT is initialized, we will start using write-combine mappings, which speeds up the scrolling considerably. Signed-off-by: Arvind Sankar Signed-off-by: Ard Biesheuvel Cc: Hans de Goede Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: linux-efi@vger.kernel.org Fixes: 69c1f396f25b ("efi/x86: Convert x86 EFI earlyprintk into generic earlycon implementation") Link: https://lkml.kernel.org/r/20191224132909.102540-2-ardb@kernel.org Signed-off-by: Ingo Molnar --- drivers/firmware/efi/earlycon.c | 16 +++++++--------- 1 file changed, 7 insertions(+), 9 deletions(-) diff --git a/drivers/firmware/efi/earlycon.c b/drivers/firmware/efi/earlycon.c index d4077db6dc97..5d4f84781aa0 100644 --- a/drivers/firmware/efi/earlycon.c +++ b/drivers/firmware/efi/earlycon.c @@ -17,7 +17,7 @@ static const struct console *earlycon_console __initdata; static const struct font_desc *font; static u32 efi_x, efi_y; static u64 fb_base; -static pgprot_t fb_prot; +static bool fb_wb; static void *efi_fb; /* @@ -33,10 +33,8 @@ static int __init efi_earlycon_remap_fb(void) if (!earlycon_console || !(earlycon_console->flags & CON_ENABLED)) return 0; - if (pgprot_val(fb_prot) == pgprot_val(PAGE_KERNEL)) - efi_fb = memremap(fb_base, screen_info.lfb_size, MEMREMAP_WB); - else - efi_fb = memremap(fb_base, screen_info.lfb_size, MEMREMAP_WC); + efi_fb = memremap(fb_base, screen_info.lfb_size, + fb_wb ? MEMREMAP_WB : MEMREMAP_WC); return efi_fb ? 0 : -ENOMEM; } @@ -53,9 +51,12 @@ late_initcall(efi_earlycon_unmap_fb); static __ref void *efi_earlycon_map(unsigned long start, unsigned long len) { + pgprot_t fb_prot; + if (efi_fb) return efi_fb + start; + fb_prot = fb_wb ? PAGE_KERNEL : pgprot_writecombine(PAGE_KERNEL); return early_memremap_prot(fb_base + start, len, pgprot_val(fb_prot)); } @@ -215,10 +216,7 @@ static int __init efi_earlycon_setup(struct earlycon_device *device, if (screen_info.capabilities & VIDEO_CAPABILITY_64BIT_BASE) fb_base |= (u64)screen_info.ext_lfb_base << 32; - if (opt && !strcmp(opt, "ram")) - fb_prot = PAGE_KERNEL; - else - fb_prot = pgprot_writecombine(PAGE_KERNEL); + fb_wb = opt && !strcmp(opt, "ram"); si = &screen_info; xres = si->lfb_width; From 818c7ce724770fbcdcd43725c81f2b3535f82b76 Mon Sep 17 00:00:00 2001 From: Hans de Goede Date: Tue, 24 Dec 2019 14:29:08 +0100 Subject: [PATCH 2/3] efi/libstub/random: Initialize pointer variables to zero for mixed mode Commit: 0d95981438c3 ("x86: efi/random: Invoke EFI_RNG_PROTOCOL to seed the UEFI RNG table") causes the drivers/efi/libstub/random.c code to get used on x86 for the first time. But this code was not written with EFI mixed mode in mind (running a 64 bit kernel on 32 bit EFI firmware), this causes the kernel to crash during early boot when running in mixed mode. The problem is that in mixed mode pointers are 64 bit, but when running on a 32 bit firmware, EFI calls which return a pointer value by reference only fill the lower 32 bits of the passed pointer, leaving the upper 32 bits uninitialized which leads to crashes. This commit fixes this by initializing pointers which are passed by reference to EFI calls to NULL before passing them, so that the upper 32 bits are initialized to 0. Signed-off-by: Hans de Goede Signed-off-by: Ard Biesheuvel Cc: Arvind Sankar Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: linux-efi@vger.kernel.org Fixes: 0d95981438c3 ("x86: efi/random: Invoke EFI_RNG_PROTOCOL to seed the UEFI RNG table") Link: https://lkml.kernel.org/r/20191224132909.102540-3-ardb@kernel.org Signed-off-by: Ingo Molnar --- drivers/firmware/efi/libstub/random.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/drivers/firmware/efi/libstub/random.c b/drivers/firmware/efi/libstub/random.c index 35edd7cfb6a1..97378cf96a2e 100644 --- a/drivers/firmware/efi/libstub/random.c +++ b/drivers/firmware/efi/libstub/random.c @@ -33,7 +33,7 @@ efi_status_t efi_get_random_bytes(efi_system_table_t *sys_table_arg, { efi_guid_t rng_proto = EFI_RNG_PROTOCOL_GUID; efi_status_t status; - struct efi_rng_protocol *rng; + struct efi_rng_protocol *rng = NULL; status = efi_call_early(locate_protocol, &rng_proto, NULL, (void **)&rng); @@ -162,8 +162,8 @@ efi_status_t efi_random_get_seed(efi_system_table_t *sys_table_arg) efi_guid_t rng_proto = EFI_RNG_PROTOCOL_GUID; efi_guid_t rng_algo_raw = EFI_RNG_ALGORITHM_RAW; efi_guid_t rng_table_guid = LINUX_EFI_RANDOM_SEED_TABLE_GUID; - struct efi_rng_protocol *rng; - struct linux_efi_random_seed *seed; + struct efi_rng_protocol *rng = NULL; + struct linux_efi_random_seed *seed = NULL; efi_status_t status; status = efi_call_early(locate_protocol, &rng_proto, NULL, From 4911ee401b7ceff8f38e0ac597cbf503d71e690c Mon Sep 17 00:00:00 2001 From: Ard Biesheuvel Date: Tue, 24 Dec 2019 14:29:09 +0100 Subject: [PATCH 3/3] x86/efistub: Disable paging at mixed mode entry The EFI mixed mode entry code goes through the ordinary startup_32() routine before jumping into the kernel's EFI boot code in 64-bit mode. The 32-bit startup code must be entered with paging disabled, but this is not documented as a requirement for the EFI handover protocol, and so we should disable paging explicitly when entering the kernel from 32-bit EFI firmware. Signed-off-by: Ard Biesheuvel Cc: Cc: Arvind Sankar Cc: Hans de Goede Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: linux-efi@vger.kernel.org Link: https://lkml.kernel.org/r/20191224132909.102540-4-ardb@kernel.org Signed-off-by: Ingo Molnar --- arch/x86/boot/compressed/head_64.S | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S index 58a512e33d8d..ee60b81944a7 100644 --- a/arch/x86/boot/compressed/head_64.S +++ b/arch/x86/boot/compressed/head_64.S @@ -244,6 +244,11 @@ SYM_FUNC_START(efi32_stub_entry) leal efi32_config(%ebp), %eax movl %eax, efi_config(%ebp) + /* Disable paging */ + movl %cr0, %eax + btrl $X86_CR0_PG_BIT, %eax + movl %eax, %cr0 + jmp startup_32 SYM_FUNC_END(efi32_stub_entry) #endif