Re: [PATCH 1/4] powerpc/64s: Fix HV NMI vs HV interrupt recoverability test

[Nicholas Piggin <npiggin@gmail.com>]

Nicholas Piggin's on January 22, 2019 4:46 pm:
> HV interrupts that use HSRR registers do not clear MSR[RI], but
> NMI entry code is not recoverable early on due to both using HSPRG
> for a scratch register.
> 
> This bug means that a system reset or machine check can cause silent
> data corruption (due to loss of r13 register) if it hits in a small
> window when taking an HV interrupt.
> 
> Fix this by marking NMIs non-recoverable if they land in HV interrupt
> ranges.

Hum, I had a v2 that I didn't send properly with a small compile fix,
but I've also just noticed this:

> +void hv_nmi_check_nonrecoverable(struct pt_regs *regs)
> +{
> +#ifdef CONFIG_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;
> +again:
> +	if (nip >= 0x500 && nip < 0x600)
> +		goto nonrecoverable;
> +	if (nip >= 0x980 && nip < 0xa00)
> +		goto nonrecoverable;
> +	if (nip >= 0xe00 && nip < 0xec0)
> +		goto nonrecoverable;
> +	if (nip >= 0xf80 && nip < 0xfa0)
> +		goto nonrecoverable;
> +	/* Trampolines are not relocated. */
> +	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;
> +	if (nip >= 0xc000000000000000ULL) {
> +		nip -= 0xc000000000000000ULL;
> +		goto again;

Tried to be a bit too clever here. The 0xc... vectors also have a 
+0x4000 offset so this won't catch them properly. I'll respin.

Thanks,
Nick