RE: [RFC PATCH V3 08/16] x86/hyperv: Initialize cpu and memory for sev-snp enlightened guest

[Michael Kelley (LINUX)]

From: Tianyu Lan <ltykernel@xxxxxxxxx> Sent: Saturday, January 21, 2023 6:46 PM
> 
> Read processor amd memory info from specific address which are
> populated by Hyper-V. Initialize smp cpu related ops, pvalidate
> system memory and add it into e820 table.
> 
> Signed-off-by: Tianyu Lan <tiala@xxxxxxxxxxxxx>
> ---
>  arch/x86/kernel/cpu/mshyperv.c | 85 ++++++++++++++++++++++++++++++++++
>  1 file changed, 85 insertions(+)
> 
> diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
> index ace5901ba0fc..b1871a7bb4c9 100644
> --- a/arch/x86/kernel/cpu/mshyperv.c
> +++ b/arch/x86/kernel/cpu/mshyperv.c
> @@ -32,6 +32,12 @@
>  #include <asm/nmi.h>
>  #include <clocksource/hyperv_timer.h>
>  #include <asm/numa.h>
> +#include <asm/coco.h>
> +#include <asm/io_apic.h>
> +#include <asm/svm.h>
> +#include <asm/sev.h>
> +#include <asm/realmode.h>
> +#include <asm/e820/api.h>
> 
>  /* Is Linux running as the root partition? */
>  bool hv_root_partition;
> @@ -251,6 +257,30 @@ static void __init hv_smp_prepare_cpus(unsigned int max_cpus)
>  }
>  #endif
> 
> +static u32 processor_count;
> +
> +static __init void hv_snp_get_smp_config(unsigned int early)
> +{
> +	if (!early) {
> +		while (num_processors < processor_count) {
> +			early_per_cpu(x86_cpu_to_apicid, num_processors) = num_processors;
> +			early_per_cpu(x86_bios_cpu_apicid, num_processors) = num_processors;
> +			physid_set(num_processors, phys_cpu_present_map);
> +			set_cpu_possible(num_processors, true);
> +			set_cpu_present(num_processors, true);
> +			num_processors++;
> +		}
> +	}
> +}
> +
> +struct memory_map_entry {
> +	u64 starting_gpn;
> +	u64 numpages;
> +	u16 type;
> +	u16 flags;
> +	u32 reserved;
> +};

Am I correct that this structure is defined by Hyper-V?  If so, it seems
like it should go in hyperv-tlfs.h, along with the definition of
EN_SEV_SNP_PROCESSOR_INFO_ADDR (which is also defined by
Hyper-V?)

> +
>  static void __init ms_hyperv_init_platform(void)
>  {
>  	int hv_max_functions_eax;
> @@ -258,6 +288,11 @@ static void __init ms_hyperv_init_platform(void)
>  	int hv_host_info_ebx;
>  	int hv_host_info_ecx;
>  	int hv_host_info_edx;
> +	struct memory_map_entry *entry;
> +	struct e820_entry *e820_entry;
> +	u64 e820_end;
> +	u64 ram_end;
> +	u64 page;
> 
>  #ifdef CONFIG_PARAVIRT
>  	pv_info.name = "Hyper-V";
> @@ -466,6 +501,56 @@ static void __init ms_hyperv_init_platform(void)
>  	if (!(ms_hyperv.features & HV_ACCESS_TSC_INVARIANT))
>  		mark_tsc_unstable("running on Hyper-V");
> 
> +	if (isolation_type_en_snp()) {

The above doesn't compile.  The function name is hv_isolation_type_en_snp().

> +		/*
> +		 * Hyper-V enlightened snp guest boots kernel
> +		 * directly without bootloader and so roms,
> +		 * bios regions and reserve resources are not
> +		 * available. Set these callback to NULL.
> +		 */
> +		x86_platform.legacy.reserve_bios_regions = x86_init_noop;
> +		x86_init.resources.probe_roms = x86_init_noop;
> +		x86_init.resources.reserve_resources = x86_init_noop;
> +		x86_init.mpparse.find_smp_config = x86_init_noop;
> +		x86_init.mpparse.get_smp_config = hv_snp_get_smp_config;
> +
> +		/*
> +		 * Hyper-V SEV-SNP enlightened guest doesn't support ioapic
> +		 * and legacy APIC page read/write. Switch to hv apic here.
> +		 */
> +		disable_ioapic_support();
> +
> +		/* Read processor number and memory layout. */
> +		processor_count = *(u32 *)__va(EN_SEV_SNP_PROCESSOR_INFO_ADDR);
> +		entry = (struct memory_map_entry *)(__va(EN_SEV_SNP_PROCESSOR_INFO_ADDR)
> +				+ sizeof(struct memory_map_entry));
> +
> +		/*
> +		 * E820 table in the memory just describes memory for
> +		 * kernel, ACPI table, cmdline, boot params and ramdisk.
> +		 * Hyper-V popoulates the rest memory layout in the EN_SEV_
> +		 * SNP_PROCESSOR_INFO_ADDR.
> +		 */
> +		for (; entry->numpages != 0; entry++) {
> +			e820_entry = &e820_table->entries[
> +					e820_table->nr_entries - 1];
> +			e820_end = e820_entry->addr + e820_entry->size;
> +			ram_end = (entry->starting_gpn +
> +				   entry->numpages) * PAGE_SIZE;
> +
> +			if (e820_end < entry->starting_gpn * PAGE_SIZE)
> +				e820_end = entry->starting_gpn * PAGE_SIZE;
> +
> +			if (e820_end < ram_end) {
> +				pr_info("Hyper-V: add e820 entry [mem %#018Lx-%#018Lx]\n", e820_end, ram_end - 1);
> +				e820__range_add(e820_end, ram_end - e820_end,
> +						E820_TYPE_RAM);
> +				for (page = e820_end; page < ram_end; page += PAGE_SIZE)
> +					pvalidate((unsigned long)__va(page), RMP_PG_SIZE_4K, true);
> +			}
> +		}
> +	}
> +

For SNP vTOM mode, most of the supporting code is placed in
arch/x86/hyperv/ivm.c, which is built only if CONFIG_HYPERV
is defined.  arch/x86/kernel/cpu/mshyperv.c is built for *any*
flavor of guest (i.e., CONFIG_HYPERVISOR_GUEST).  I'm thinking
all this code should go as a supporting function in ivm.c, to
avoid overloading mshyperv.c.  Take a look at how hv_vtom_init()
is handled in my patch set.

Breaking it out as a separate supporting function might also
help reduce the deep indentation problem a bit. :-)

>  	hardlockup_detector_disable();
>  }
> 
> --
> 2.25.1