arch/x86/hyperv/hv_vtl.c | 31 +++++++++++++++++++++++++++++++ 1 file changed, 31 insertions(+)
The first patch defines a specialized machine emergency restart callback not to write to the physical address of 0x472 which is what the native_machine_emergency_restart() does unconditionally. I first wanted to tweak that function[1], and in the course of the discussion it looked as the risks of doing that would outweigh the benefit: the bare-metal systems have likely adopted that behavior as a standard although I could not find any mentions of that magic address in the UEFI+ACPI specification. The second patch removes the need to always supply "reboot=t" to the kernel command line in the OpenHCL bootloader [2]. There is no other option at the moment; when/if it appears the newly added callback's code can be adjusted as required. It would be great to apply this to the stable tree if no concerns, should apply cleanly. [1] https://lore.kernel.org/all/20250109204352.1720337-1-romank@linux.microsoft.com/ [2] https://github.com/microsoft/openvmm/blob/7a9d0e0a00461be6e5f3267af9ea54cc7157c900/openhcl/openhcl_boot/src/main.rs#L139 Roman Kisel (2): x86/hyperv: VTL mode emergency restart callback x86/hyperv: VTL mode callback for restarting the system arch/x86/hyperv/hv_vtl.c | 31 +++++++++++++++++++++++++++++++ 1 file changed, 31 insertions(+) base-commit: 2e03358be78b65d28b66e17aca9e0c8700b0df78 -- 2.34.1
On Fri, Jan 17, 2025 at 01:07:00PM -0800, Roman Kisel wrote: > The first patch defines a specialized machine emergency restart > callback not to write to the physical address of 0x472 which is > what the native_machine_emergency_restart() does unconditionally. > > I first wanted to tweak that function[1], and in the course of > the discussion it looked as the risks of doing that would > outweigh the benefit: the bare-metal systems have likely adopted > that behavior as a standard although I could not find any mentions > of that magic address in the UEFI+ACPI specification. > > The second patch removes the need to always supply "reboot=t" > to the kernel command line in the OpenHCL bootloader [2]. There is > no other option at the moment; when/if it appears the newly added > callback's code can be adjusted as required. > > It would be great to apply this to the stable tree if no concerns, > should apply cleanly. > > [1] https://lore.kernel.org/all/20250109204352.1720337-1-romank@linux.microsoft.com/ > [2] https://github.com/microsoft/openvmm/blob/7a9d0e0a00461be6e5f3267af9ea54cc7157c900/openhcl/openhcl_boot/src/main.rs#L139 > > Roman Kisel (2): > x86/hyperv: VTL mode emergency restart callback > x86/hyperv: VTL mode callback for restarting the system Saurabh please review these patches. Thanks. I don't have a strong opinion on them. > > arch/x86/hyperv/hv_vtl.c | 31 +++++++++++++++++++++++++++++++ > 1 file changed, 31 insertions(+) > > > base-commit: 2e03358be78b65d28b66e17aca9e0c8700b0df78 > -- > 2.34.1 >
On Wed, Feb 12, 2025 at 02:21:18AM +0000, Wei Liu wrote: > On Fri, Jan 17, 2025 at 01:07:00PM -0800, Roman Kisel wrote: > > The first patch defines a specialized machine emergency restart > > callback not to write to the physical address of 0x472 which is > > what the native_machine_emergency_restart() does unconditionally. > > > > I first wanted to tweak that function[1], and in the course of > > the discussion it looked as the risks of doing that would > > outweigh the benefit: the bare-metal systems have likely adopted > > that behavior as a standard although I could not find any mentions > > of that magic address in the UEFI+ACPI specification. > > > > The second patch removes the need to always supply "reboot=t" > > to the kernel command line in the OpenHCL bootloader [2]. There is > > no other option at the moment; when/if it appears the newly added > > callback's code can be adjusted as required. > > > > It would be great to apply this to the stable tree if no concerns, > > should apply cleanly. > > > > [1] https://lore.kernel.org/all/20250109204352.1720337-1-romank@linux.microsoft.com/ > > [2] https://github.com/microsoft/openvmm/blob/7a9d0e0a00461be6e5f3267af9ea54cc7157c900/openhcl/openhcl_boot/src/main.rs#L139 > > > > Roman Kisel (2): > > x86/hyperv: VTL mode emergency restart callback > > x86/hyperv: VTL mode callback for restarting the system > > Saurabh please review these patches. Thanks. Hi Roman, Thanks for the patch, few suggestions and queries: 1. Please fix the kernel bot warning 2. Cc Stable tree is not enough, you need to mention the "Fixes" tag as well for the commit upto where you want this patch to be backported. 3. In your 2/2 commit, you mention 'triple fault' is the only way to reboot in x86. Is that accurate ? Do you mean to say OpenHCL/VTL here ? If this behaviour is specific to OpenHCl and not VTLs in general, is there a way we can make these changes only for OpenHCL. - Saurabh > > I don't have a strong opinion on them. > > > > > arch/x86/hyperv/hv_vtl.c | 31 +++++++++++++++++++++++++++++++ > > 1 file changed, 31 insertions(+) > > > > > > base-commit: 2e03358be78b65d28b66e17aca9e0c8700b0df78 > > -- > > 2.34.1 > >
On 2/12/2025 9:54 AM, Saurabh Singh Sengar wrote: > On Wed, Feb 12, 2025 at 02:21:18AM +0000, Wei Liu wrote: [...] >> >> Saurabh please review these patches. Thanks. > > Hi Roman, Hi Saurabh, > > Thanks for the patch, few suggestions and queries: > > 1. Please fix the kernel bot warning Will do! > 2. Cc Stable tree is not enough, you need to mention the "Fixes" tag as well > for the commit upto where you want this patch to be backported. Understood, thanks! > 3. In your 2/2 commit, you mention 'triple fault' is the only way to reboot in x86. > Is that accurate ? Do you mean to say OpenHCL/VTL here ? > If this behaviour is specific to OpenHCl and not VTLs in general, is there a way > we can make these changes only for OpenHCL. Right, I meant OpenHCL/VTL2, thank you very much! The changes are scoped to running in VTLs in general at the moment. I can add a check for the VTL == 2 if you'd like me to. For VTL1 (aka LVBS), maybe folks would like to do something else, do you happen to know? Maybe to report that to the VTL0 guest kernel although seems dubious: the higher VTL failed so the lights must be out for the lower VTLs? Or kexec? > > > - Saurabh > >> >> I don't have a strong opinion on them. >> >>> >>> arch/x86/hyperv/hv_vtl.c | 31 +++++++++++++++++++++++++++++++ >>> 1 file changed, 31 insertions(+) >>> >>> >>> base-commit: 2e03358be78b65d28b66e17aca9e0c8700b0df78 >>> -- >>> 2.34.1 >>> -- Thank you, Roman
On Wed, Feb 12, 2025 at 02:56:43PM -0800, Roman Kisel wrote: > > > On 2/12/2025 9:54 AM, Saurabh Singh Sengar wrote: > >On Wed, Feb 12, 2025 at 02:21:18AM +0000, Wei Liu wrote: > [...] > >> > >>Saurabh please review these patches. Thanks. > > > >Hi Roman, > Hi Saurabh, > > > > >Thanks for the patch, few suggestions and queries: > > > >1. Please fix the kernel bot warning > Will do! > > >2. Cc Stable tree is not enough, you need to mention the "Fixes" tag as well > > for the commit upto where you want this patch to be backported. > Understood, thanks! > > >3. In your 2/2 commit, you mention 'triple fault' is the only way to reboot in x86. > > Is that accurate ? Do you mean to say OpenHCL/VTL here ? > > If this behaviour is specific to OpenHCl and not VTLs in general, is there a way > > we can make these changes only for OpenHCL. > Right, I meant OpenHCL/VTL2, thank you very much! The changes are scoped > to running in VTLs in general at the moment. I can add a check for the > VTL == 2 if you'd like me to. > > For VTL1 (aka LVBS), maybe folks would like to do something else, > do you happen to know? Maybe to report that to the VTL0 guest kernel > although seems dubious: the higher VTL failed so the lights must be out > for the lower VTLs? Or kexec? I am not aware of LVBS plans, and as far as I consider OpenVMM the only current user of this VTL code. I recommend keeping the code as simple as possible unless there is a clear use case for additional complexity. It would be helpful to include these details in a comment so that future users of this file can understand and modify it as needed. - Saurabh > > > > >- Saurabh > > > >> > >>I don't have a strong opinion on them. > >> > >>> > >>> arch/x86/hyperv/hv_vtl.c | 31 +++++++++++++++++++++++++++++++ > >>> 1 file changed, 31 insertions(+) > >>> > >>> > >>>base-commit: 2e03358be78b65d28b66e17aca9e0c8700b0df78 > >>>-- > >>>2.34.1 > >>> > > -- > Thank you, > Roman >
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