[ Adding Greg and Kamal ] On Wed, Jan 06, 2016 at 01:31:55PM +0000, Matt Fleming wrote: > On Wed, 06 Jan, at 11:24:55AM, Luis Henriques wrote: > > On Wed, Jan 06, 2016 at 11:00:31AM +0000, Matt Fleming wrote: > > > On Wed, 06 Jan, at 11:47:20AM, Paolo Bonzini wrote: > > > > > > > > Without testing the problematic scenario explicitly (32-bit UEFI > > > > kernel), I think this patch and 26/91 should not be backported to > > > > kernels that do not have 23a0d4e8fa6d. > > > > > > I tend to agree. > > > > I can see these 2 commits in kernels as old as 3.10 (which definitely do > > not include 23a0d4e8fa6d). Does this mean these should be reverted from > > stable kernels that already include these patches? Or would you rather > > recommend to backport 23a0d4e8fa6d? > > That depends on your appetite for risk ;-) > Heh, I guess stable kernels aren't really about appetite for risk :-) > 23a0d4e8fa6d does fix a legitimate bug, albeit one that no one seems > to have ever hit. Personally, I'd go for backporting 23a0d4e8fa6d. This commit doesn't seem to be too bad to backport. I'm attaching 2 backports: - one is for the 3.16 stable kernel, - the other can be applied to 3.10, 3.12 and 3.13 (For the other kernels, I believe 23a0d4e8fa6d will be a clean cherry-pick.) Cheers, -- Luís
>From 6b58a852d51e7d1991d759c331bc276b2461c4c3 Mon Sep 17 00:00:00 2001 From: Ingo Molnar <mingo@xxxxxxxxxx> Date: Tue, 3 Mar 2015 07:34:33 +0100 Subject: efi: Disable interrupts around EFI calls, not in the epilog/prolog calls commit 23a0d4e8fa6d3a1d7fb819f79bcc0a3739c30ba9 upstream. Tapasweni Pathak reported that we do a kmalloc() in efi_call_phys_prolog() on x86-64 while having interrupts disabled, which is a big no-no, as kmalloc() can sleep. Solve this by removing the irq disabling from the prolog/epilog calls around EFI calls: it's unnecessary, as in this stage we are single threaded in the boot thread, and we don't ever execute this from interrupt contexts. Reported-by: Tapasweni Pathak <tapaswenipathak@xxxxxxxxx> Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> Signed-off-by: Matt Fleming <matt.fleming@xxxxxxxxx> [ luis: backported to 3.10: adjusted context ] Signed-off-by: Luis Henriques <luis.henriques@xxxxxxxxxxxxx> --- arch/x86/platform/efi/efi.c | 7 +++++++ arch/x86/platform/efi/efi_32.c | 11 +++-------- arch/x86/platform/efi/efi_64.c | 3 --- 3 files changed, 10 insertions(+), 11 deletions(-) diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c index 6033be9ff81a..3c8bffdc71c8 100644 --- a/arch/x86/platform/efi/efi.c +++ b/arch/x86/platform/efi/efi.c @@ -250,12 +250,19 @@ static efi_status_t __init phys_efi_set_virtual_address_map( efi_memory_desc_t *virtual_map) { efi_status_t status; + unsigned long flags; efi_call_phys_prelog(); + + /* Disable interrupts around EFI calls: */ + local_irq_save(flags); status = efi_call_phys4(efi_phys.set_virtual_address_map, memory_map_size, descriptor_size, descriptor_version, virtual_map); + local_irq_restore(flags); + efi_call_phys_epilog(); + return status; } diff --git a/arch/x86/platform/efi/efi_32.c b/arch/x86/platform/efi/efi_32.c index 40e446941dd7..bebbee05e331 100644 --- a/arch/x86/platform/efi/efi_32.c +++ b/arch/x86/platform/efi/efi_32.c @@ -33,19 +33,16 @@ /* * To make EFI call EFI runtime service in physical addressing mode we need - * prelog/epilog before/after the invocation to disable interrupt, to - * claim EFI runtime service handler exclusively and to duplicate a memory in - * low memory space say 0 - 3G. + * prolog/epilog before/after the invocation to claim the EFI runtime service + * handler exclusively and to duplicate a memory mapping in low memory space, + * say 0 - 3G. */ -static unsigned long efi_rt_eflags; void efi_call_phys_prelog(void) { struct desc_ptr gdt_descr; - local_irq_save(efi_rt_eflags); - load_cr3(initial_page_table); __flush_tlb_all(); @@ -64,6 +61,4 @@ void efi_call_phys_epilog(void) load_cr3(swapper_pg_dir); __flush_tlb_all(); - - local_irq_restore(efi_rt_eflags); } diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c index 39a0e7f1f0a3..2f6c1a9734c8 100644 --- a/arch/x86/platform/efi/efi_64.c +++ b/arch/x86/platform/efi/efi_64.c @@ -40,7 +40,6 @@ #include <asm/fixmap.h> static pgd_t *save_pgd __initdata; -static unsigned long efi_flags __initdata; static void __init early_code_mapping_set_exec(int executable) { @@ -66,7 +65,6 @@ void __init efi_call_phys_prelog(void) int n_pgds; early_code_mapping_set_exec(1); - local_irq_save(efi_flags); n_pgds = DIV_ROUND_UP((max_pfn << PAGE_SHIFT), PGDIR_SIZE); save_pgd = kmalloc(n_pgds * sizeof(pgd_t), GFP_KERNEL); @@ -90,7 +88,6 @@ void __init efi_call_phys_epilog(void) set_pgd(pgd_offset_k(pgd * PGDIR_SIZE), save_pgd[pgd]); kfree(save_pgd); __flush_tlb_all(); - local_irq_restore(efi_flags); early_code_mapping_set_exec(0); }
>From 466b891857a536af2a9b7ad058e1cc00b702a528 Mon Sep 17 00:00:00 2001 From: Ingo Molnar <mingo@xxxxxxxxxx> Date: Tue, 3 Mar 2015 07:34:33 +0100 Subject: [PATCH] efi: Disable interrupts around EFI calls, not in the epilog/prolog calls commit 23a0d4e8fa6d3a1d7fb819f79bcc0a3739c30ba9 upstream. Tapasweni Pathak reported that we do a kmalloc() in efi_call_phys_prolog() on x86-64 while having interrupts disabled, which is a big no-no, as kmalloc() can sleep. Solve this by removing the irq disabling from the prolog/epilog calls around EFI calls: it's unnecessary, as in this stage we are single threaded in the boot thread, and we don't ever execute this from interrupt contexts. Reported-by: Tapasweni Pathak <tapaswenipathak@xxxxxxxxx> Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> Signed-off-by: Matt Fleming <matt.fleming@xxxxxxxxx> [ luis: backported to 3.16: adjusted context ] Signed-off-by: Luis Henriques <luis.henriques@xxxxxxxxxxxxx> --- arch/x86/platform/efi/efi.c | 7 +++++++ arch/x86/platform/efi/efi_32.c | 11 +++-------- arch/x86/platform/efi/efi_64.c | 3 --- 3 files changed, 10 insertions(+), 11 deletions(-) diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c index 5bbb477f5c2a..09c8ac286cd5 100644 --- a/arch/x86/platform/efi/efi.c +++ b/arch/x86/platform/efi/efi.c @@ -236,12 +236,19 @@ static efi_status_t __init phys_efi_set_virtual_address_map( efi_memory_desc_t *virtual_map) { efi_status_t status; + unsigned long flags; efi_call_phys_prelog(); + + /* Disable interrupts around EFI calls: */ + local_irq_save(flags); status = efi_call_phys(efi_phys.set_virtual_address_map, memory_map_size, descriptor_size, descriptor_version, virtual_map); + local_irq_restore(flags); + efi_call_phys_epilog(); + return status; } diff --git a/arch/x86/platform/efi/efi_32.c b/arch/x86/platform/efi/efi_32.c index 9ee3491e31fb..be4e7eb41674 100644 --- a/arch/x86/platform/efi/efi_32.c +++ b/arch/x86/platform/efi/efi_32.c @@ -33,11 +33,10 @@ /* * To make EFI call EFI runtime service in physical addressing mode we need - * prelog/epilog before/after the invocation to disable interrupt, to - * claim EFI runtime service handler exclusively and to duplicate a memory in - * low memory space say 0 - 3G. + * prolog/epilog before/after the invocation to claim the EFI runtime service + * handler exclusively and to duplicate a memory mapping in low memory space, + * say 0 - 3G. */ -static unsigned long efi_rt_eflags; void efi_sync_low_kernel_mappings(void) {} void __init efi_dump_pagetable(void) {} @@ -59,8 +58,6 @@ void efi_call_phys_prelog(void) { struct desc_ptr gdt_descr; - local_irq_save(efi_rt_eflags); - load_cr3(initial_page_table); __flush_tlb_all(); @@ -79,8 +76,6 @@ void efi_call_phys_epilog(void) load_cr3(swapper_pg_dir); __flush_tlb_all(); - - local_irq_restore(efi_rt_eflags); } void __init efi_runtime_mkexec(void) diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c index 290d397e1dd9..8139b4858403 100644 --- a/arch/x86/platform/efi/efi_64.c +++ b/arch/x86/platform/efi/efi_64.c @@ -42,7 +42,6 @@ #include <asm/time.h> static pgd_t *save_pgd __initdata; -static unsigned long efi_flags __initdata; /* * We allocate runtime services regions bottom-up, starting from -4G, i.e. @@ -89,7 +88,6 @@ void __init efi_call_phys_prelog(void) return; early_code_mapping_set_exec(1); - local_irq_save(efi_flags); n_pgds = DIV_ROUND_UP((max_pfn << PAGE_SHIFT), PGDIR_SIZE); save_pgd = kmalloc(n_pgds * sizeof(pgd_t), GFP_KERNEL); @@ -117,7 +115,6 @@ void __init efi_call_phys_epilog(void) set_pgd(pgd_offset_k(pgd * PGDIR_SIZE), save_pgd[pgd]); kfree(save_pgd); __flush_tlb_all(); - local_irq_restore(efi_flags); early_code_mapping_set_exec(0); }