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Re: [Qemu-devel] [PATCH] spapr: don't initialize PATB entry if max-cpu-c
From: |
David Gibson |
Subject: |
Re: [Qemu-devel] [PATCH] spapr: don't initialize PATB entry if max-cpu-compat < power9 |
Date: |
Fri, 15 Dec 2017 09:50:41 +1100 |
User-agent: |
Mutt/1.9.1 (2017-09-22) |
On Thu, Dec 14, 2017 at 07:09:48PM +0100, Laurent Vivier wrote:
> if KVM is enabled and KVM capabilities MMU radix is available,
> the partition table entry (patb_entry) for the radix mode is
> initialized by default in ppc_spapr_reset().
>
> It's a problem if we want to migrate the guest to a POWER8 host
> while the kernel is not started to set the value to the one
> expected for a POWER8 CPU.
>
> The "-machine max-cpu-compat=power8" should allow to migrate
> a POWER9 KVM host to a POWER8 KVM host, but because patb_entry
> is set, the destination QEMU tries to enable radix mode on the
> POWER8 host. This fails and cancels the migration:
>
> Process table config unsupported by the host
> error while loading state for instance 0x0 of device 'spapr'
> load of migration failed: Invalid argument
>
> This patch doesn't set the PATB entry if the user provides
> a CPU compatibility mode that doesn't support radix mode.
>
> Signed-off-by: Laurent Vivier <address@hidden>
Applied to ppc-for-2.12.
> ---
> hw/ppc/spapr.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> index 1ac7eb0f8c..66d0ed5256 100644
> --- a/hw/ppc/spapr.c
> +++ b/hw/ppc/spapr.c
> @@ -1440,7 +1440,10 @@ static void ppc_spapr_reset(void)
> /* Check for unknown sysbus devices */
> foreach_dynamic_sysbus_device(find_unknown_sysbus_device, NULL);
>
> - if (kvm_enabled() && kvmppc_has_cap_mmu_radix()) {
> + first_ppc_cpu = POWERPC_CPU(first_cpu);
> + if (kvm_enabled() && kvmppc_has_cap_mmu_radix() &&
> + ppc_check_compat(first_ppc_cpu, CPU_POWERPC_LOGICAL_3_00, 0,
> + spapr->max_compat_pvr)) {
> /* If using KVM with radix mode available, VCPUs can be started
> * without a HPT because KVM will start them in radix mode.
> * Set the GR bit in PATB so that we know there is no HPT. */
> @@ -1499,7 +1502,6 @@ static void ppc_spapr_reset(void)
> g_free(fdt);
>
> /* Set up the entry state */
> - first_ppc_cpu = POWERPC_CPU(first_cpu);
> first_ppc_cpu->env.gpr[3] = fdt_addr;
> first_ppc_cpu->env.gpr[5] = 0;
> first_cpu->halted = 0;
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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