Commit ccd47702 authored by Nicholas Piggin's avatar Nicholas Piggin Committed by Michael Ellerman
Browse files

powerpc/64s: Fix HV NMI vs HV interrupt recoverability test 



HV interrupts that use HSRR registers do not enter with MSR[RI] clear,
but their entry code is not recoverable vs NMI, due to shared use of
HSPRG1 as a scratch register to save r13.

This means that a system reset or machine check that hits in HSRR
interrupt entry can cause r13 to be silently corrupted.

Fix this by marking NMIs non-recoverable if they land in HV interrupt
ranges.

Signed-off-by: default avatarNicholas Piggin <npiggin@gmail.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
parent 3b4d07d2

arch/powerpc/include/asm/asm-prototypes.h

+8 −0
Original line number Diff line number Diff line
@@ -51,6 +51,14 @@ int exit_vmx_usercopy(void); 
int enter_vmx_ops(void);

void *exit_vmx_ops(void *dest);



/* Exceptions */

#ifdef CONFIG_PPC_POWERNV

extern unsigned long real_trampolines_start;

extern unsigned long real_trampolines_end;

extern unsigned long virt_trampolines_start;

extern unsigned long virt_trampolines_end;

#endif



/* Traps */

long machine_check_early(struct pt_regs *regs);

long hmi_exception_realmode(struct pt_regs *regs);

arch/powerpc/include/asm/nmi.h

+2 −0
Original line number Diff line number Diff line
@@ -14,4 +14,6 @@ extern void arch_trigger_cpumask_backtrace(const cpumask_t *mask, 
#define arch_trigger_cpumask_backtrace arch_trigger_cpumask_backtrace

#endif



extern void hv_nmi_check_nonrecoverable(struct pt_regs *regs);



#endif /* _ASM_NMI_H */

arch/powerpc/kernel/exceptions-64s.S

+8 −0
Original line number Diff line number Diff line
@@ -68,6 +68,14 @@ OPEN_FIXED_SECTION(real_vectors, 0x0100, 0x1900) 
OPEN_FIXED_SECTION(real_trampolines,    0x1900, 0x4000)

OPEN_FIXED_SECTION(virt_vectors,        0x4000, 0x5900)

OPEN_FIXED_SECTION(virt_trampolines,    0x5900, 0x7000)



#ifdef CONFIG_PPC_POWERNV

	.globl real_trampolines_start

	.globl real_trampolines_end

	.globl virt_trampolines_start

	.globl virt_trampolines_end

#endif



#if defined(CONFIG_PPC_PSERIES) || defined(CONFIG_PPC_POWERNV)

/*

 * Data area reserved for FWNMI option.

arch/powerpc/kernel/mce.c

+3 −0
Original line number Diff line number Diff line
@@ -31,6 +31,7 @@ 


#include <asm/machdep.h>

#include <asm/mce.h>

#include <asm/nmi.h>



static DEFINE_PER_CPU(int, mce_nest_count);

static DEFINE_PER_CPU(struct machine_check_event[MAX_MC_EVT], mce_event);
@@ -490,6 +491,8 @@ long machine_check_early(struct pt_regs *regs) 
{

	long handled = 0;



	hv_nmi_check_nonrecoverable(regs);



	/*

	 * See if platform is capable of handling machine check.

	 */

arch/powerpc/kernel/traps.c

+66 −0
Original line number Diff line number Diff line
@@ -369,6 +369,70 @@ void _exception(int signr, struct pt_regs *regs, int code, unsigned long addr) 
	force_sig_fault(signr, code, (void __user *)addr, current);

}



/*

 * The interrupt architecture has a quirk in that the HV interrupts excluding

 * the NMIs (0x100 and 0x200) do not clear MSR[RI] at entry. The first thing

 * that an interrupt handler must do is save off a GPR into a scratch register,

 * and all interrupts on POWERNV (HV=1) use the HSPRG1 register as scratch.

 * Therefore an NMI can clobber an HV interrupt's live HSPRG1 without noticing

 * that it is non-reentrant, which leads to random data corruption.

 *

 * The solution is for NMI interrupts in HV mode to check if they originated

 * from these critical HV interrupt regions. If so, then mark them not

 * recoverable.

 *

 * An alternative would be for HV NMIs to use SPRG for scratch to avoid the

 * HSPRG1 clobber, however this would cause guest SPRG to be clobbered. Linux

 * guests should always have MSR[RI]=0 when its scratch SPRG is in use, so

 * that would work. However any other guest OS that may have the SPRG live

 * and MSR[RI]=1 could encounter silent corruption.

 *

 * Builds that do not support KVM could take this second option to increase

 * the recoverability of NMIs.

 */

void hv_nmi_check_nonrecoverable(struct pt_regs *regs)

{

#ifdef CONFIG_PPC_POWERNV

	unsigned long kbase = (unsigned long)_stext;

	unsigned long nip = regs->nip;



	if (!(regs->msr & MSR_RI))

		return;

	if (!(regs->msr & MSR_HV))

		return;

	if (regs->msr & MSR_PR)

		return;



	/*

	 * Now test if the interrupt has hit a range that may be using

	 * HSPRG1 without having RI=0 (i.e., an HSRR interrupt). The

	 * problem ranges all run un-relocated. Test real and virt modes

	 * at the same time by droping the high bit of the nip (virt mode

	 * entry points still have the +0x4000 offset).

	 */

	nip &= ~0xc000000000000000ULL;

	if ((nip >= 0x500 && nip < 0x600) || (nip >= 0x4500 && nip < 0x4600))

		goto nonrecoverable;

	if ((nip >= 0x980 && nip < 0xa00) || (nip >= 0x4980 && nip < 0x4a00))

		goto nonrecoverable;

	if ((nip >= 0xe00 && nip < 0xec0) || (nip >= 0x4e00 && nip < 0x4ec0))

		goto nonrecoverable;

	if ((nip >= 0xf80 && nip < 0xfa0) || (nip >= 0x4f80 && nip < 0x4fa0))

		goto nonrecoverable;

	/* Trampoline code runs un-relocated so subtract kbase. */

	if (nip >= real_trampolines_start - kbase &&

			nip < real_trampolines_end - kbase)

		goto nonrecoverable;

	if (nip >= virt_trampolines_start - kbase &&

			nip < virt_trampolines_end - kbase)

		goto nonrecoverable;

	return;



nonrecoverable:

	regs->msr &= ~MSR_RI;

#endif

}



void system_reset_exception(struct pt_regs *regs)

{

	/*
@@ -379,6 +443,8 @@ void system_reset_exception(struct pt_regs *regs) 
	if (!nested)

		nmi_enter();



	hv_nmi_check_nonrecoverable(regs);



	__this_cpu_inc(irq_stat.sreset_irqs);



	/* See if any machine dependent calls */

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