Re: [PATCH v8 0/3] Poisoned memory recovery on reboot

[Peter Xu <peterx@redhat.com>]

On Tue, Feb 11, 2025 at 09:27:04PM +0000, “William Roche wrote:
> From: William Roche <william.roche@oracle.com>
> 
> Here is a very simplified version of my fix only dealing with the
> recovery of huge pages on VM reset.
>  ---
> This set of patches fixes an existing bug with hardware memory errors
> impacting hugetlbfs memory backed VMs and its recovery on VM reset.
> When using hugetlbfs large pages, any large page location being impacted
> by an HW memory error results in poisoning the entire page, suddenly
> making a large chunk of the VM memory unusable.
> 
> The main problem that currently exists in Qemu is the lack of backend
> file repair before resetting the VM memory, resulting in the impacted
> memory to be silently unusable even after a VM reboot.
> 
> In order to fix this issue, we take into account the page size of the
> impacted memory block when dealing with the associated poisoned page
> location.
> 
> Using the page size information we also try to regenerate the memory
> calling ram_block_discard_range() on VM reset when running
> qemu_ram_remap(). So that a poisoned memory backed by a hugetlbfs
> file is regenerated with a hole punched in this file. A new page is
> loaded when the location is first touched.  In case of a discard
> failure we fall back to remapping the memory location.
> 
> But we currently don't reset the memory settings and the 'prealloc'
> attribute is ignored after the remap from the file backend.

queued patch 1-2, thanks.

-- 
Peter Xu