Messages in this thread | | | Date | Mon, 2 Oct 2023 17:41:02 -0700 | Subject | Re: [PATCH v4 14/15] asm-generic: hyperv: Use new Hyper-V headers conditionally. | From | Nuno Das Neves <> |
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Hi Alex,
On 10/2/2023 12:35 PM, Alex Ionescu wrote: > Hi Nuno, > > I understand the requirement to have > undocumented/non-standard/non-TLFS-published information in the HDK > headers, however, the current state of this patch is that for any > other code that's not in the kernel today, or in this upcoming driver, > the hyperv-tlfs definitions are incomplete, because some *documented* > TLFS fields are only in HDK headers. Similarly, it is also impossible
If I understand correctly, you are saying there are documented definitions (in the TLFS document), which are NOT in hyperv-tlfs.h, but ARE in these new HDK headers, correct?
If these are needed elsewhere in the kernel, they can just be added to hyperv-tlfs.h.
> to only use the HDK headers for other use cases, because some basic > documented, standard defines only exist in hyperv-tlfs. So there is no > "logical" relationship between the two -- HDK headers are not _just_ > undocumented information, but also documented information, but also > not complete documented information.
That is correct - they are meant to be independently compileable. The new HDK headers only serve as a replacement *in our driver* when we need some definitions like do_hypercall() etc in mshyperv.h.
> > Would you consider: > > 1) Updating hyperv-tlfs with all newly documented TLFS fields that are > in the HDK headers?
I think this can be done on an as-needed basis, as I outlined above.
> OR > 2) Updating the new HDK headers you're adding here to also include > previously-documented information from hyperv-tlfs? This way, someone > can include the HDK headers and get everything they need
The new HDK headers are only intended for the new mshv driver.
> OR > 3) Truly making hypertv-tlfs the "documented" header, and then > removing any duplication from HDK so that it remains the > "undocumented" header file. In this manner, one would include > hyperv-tlfs to use the stable ABI, and they would include HDK (which > would include hyperv-tlfs) to use the unstable+stable ABI.
hyperv-tlfs.h is remaining the "documented" header.
But, we can't make the HDK header depend on hyperv-tlfs.h, for 2 primary reasons: 1. We need to put the new HDK headers in uapi so that we can use them in our IOCTL interface. As a result, we can't include hyperv-tlfs.h (unless we put it in uapi as well). 2. The HDK headers not only duplicate, but also MODIFY some structures in hyperv-tlfs.h. e.g., The struct is in hyperv-tlfs.h, but a particular field or bitfield is not.
Thanks, Nuno
> > Thank you for your consideration. > > Best regards, > Alex Ionescu > > On Fri, Sep 29, 2023 at 2:02 PM Nuno Das Neves > <nunodasneves@linux.microsoft.com> wrote: >> >> Add asm-generic/hyperv-defs.h. It includes hyperv-tlfs.h or hvhdk.h >> depending on compile-time constant HV_HYPERV_DEFS which will be defined in >> the mshv driver. >> >> This is needed to keep unstable Hyper-V interfaces independent of >> hyperv-tlfs.h. This ensures hvhdk.h replaces hyperv-tlfs.h in the mshv >> driver, even via indirect includes. >> >> Signed-off-by: Nuno Das Neves <nunodasneves@linux.microsoft.com> >> Acked-by: Wei Liu <wei.liu@kernel.org> >> --- >> arch/arm64/include/asm/mshyperv.h | 2 +- >> arch/x86/include/asm/mshyperv.h | 3 +-- >> drivers/hv/hyperv_vmbus.h | 1 - >> include/asm-generic/hyperv-defs.h | 26 ++++++++++++++++++++++++++ >> include/asm-generic/mshyperv.h | 2 +- >> include/linux/hyperv.h | 2 +- >> 6 files changed, 30 insertions(+), 6 deletions(-) >> create mode 100644 include/asm-generic/hyperv-defs.h >> >> diff --git a/arch/arm64/include/asm/mshyperv.h b/arch/arm64/include/asm/mshyperv.h >> index 20070a847304..8ec14caf3d4f 100644 >> --- a/arch/arm64/include/asm/mshyperv.h >> +++ b/arch/arm64/include/asm/mshyperv.h >> @@ -20,7 +20,7 @@ >> >> #include <linux/types.h> >> #include <linux/arm-smccc.h> >> -#include <asm/hyperv-tlfs.h> >> +#include <asm-generic/hyperv-defs.h> >> >> /* >> * Declare calls to get and set Hyper-V VP register values on ARM64, which >> diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h >> index e3768d787065..bb1b97106cd3 100644 >> --- a/arch/x86/include/asm/mshyperv.h >> +++ b/arch/x86/include/asm/mshyperv.h >> @@ -6,10 +6,9 @@ >> #include <linux/nmi.h> >> #include <linux/msi.h> >> #include <linux/io.h> >> -#include <asm/hyperv-tlfs.h> >> #include <asm/nospec-branch.h> >> #include <asm/paravirt.h> >> -#include <asm/mshyperv.h> >> +#include <asm-generic/hyperv-defs.h> >> >> /* >> * Hyper-V always provides a single IO-APIC at this MMIO address. >> diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h >> index 09792eb4ffed..0e4bc18a13fa 100644 >> --- a/drivers/hv/hyperv_vmbus.h >> +++ b/drivers/hv/hyperv_vmbus.h >> @@ -15,7 +15,6 @@ >> #include <linux/list.h> >> #include <linux/bitops.h> >> #include <asm/sync_bitops.h> >> -#include <asm/hyperv-tlfs.h> >> #include <linux/atomic.h> >> #include <linux/hyperv.h> >> #include <linux/interrupt.h> >> diff --git a/include/asm-generic/hyperv-defs.h b/include/asm-generic/hyperv-defs.h >> new file mode 100644 >> index 000000000000..ac6fcba35c8c >> --- /dev/null >> +++ b/include/asm-generic/hyperv-defs.h >> @@ -0,0 +1,26 @@ >> +/* SPDX-License-Identifier: GPL-2.0 */ >> +#ifndef _ASM_GENERIC_HYPERV_DEFS_H >> +#define _ASM_GENERIC_HYPERV_DEFS_H >> + >> +/* >> + * There are cases where Microsoft Hypervisor ABIs are needed which may not be >> + * stable or present in the Hyper-V TLFS document. E.g. the mshv_root driver. >> + * >> + * As these interfaces are unstable and may differ from hyperv-tlfs.h, they >> + * must be kept separate and independent. >> + * >> + * However, code from files that depend on hyperv-tlfs.h (such as mshyperv.h) >> + * is still needed, so work around the issue by conditionally including the >> + * correct definitions. >> + * >> + * Note: Since they are independent of each other, there are many definitions >> + * duplicated in both hyperv-tlfs.h and uapi/hyperv/hv*.h files. >> + */ >> +#ifdef HV_HYPERV_DEFS >> +#include <uapi/hyperv/hvhdk.h> >> +#else >> +#include <asm/hyperv-tlfs.h> >> +#endif >> + >> +#endif /* _ASM_GENERIC_HYPERV_DEFS_H */ >> + >> diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h >> index d832852d0ee7..6bef0d59d1b7 100644 >> --- a/include/asm-generic/mshyperv.h >> +++ b/include/asm-generic/mshyperv.h >> @@ -25,7 +25,7 @@ >> #include <linux/cpumask.h> >> #include <linux/nmi.h> >> #include <asm/ptrace.h> >> -#include <asm/hyperv-tlfs.h> >> +#include <asm-generic/hyperv-defs.h> >> >> #define VTPM_BASE_ADDRESS 0xfed40000 >> >> diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h >> index 4d5a5e39d76c..722a8cf23d87 100644 >> --- a/include/linux/hyperv.h >> +++ b/include/linux/hyperv.h >> @@ -24,7 +24,7 @@ >> #include <linux/mod_devicetable.h> >> #include <linux/interrupt.h> >> #include <linux/reciprocal_div.h> >> -#include <asm/hyperv-tlfs.h> >> +#include <asm-generic/hyperv-defs.h> >> >> #define MAX_PAGE_BUFFER_COUNT 32 >> #define MAX_MULTIPAGE_BUFFER_COUNT 32 /* 128K */ >> -- >> 2.25.1 >> >>
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