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Tue, 26 Mar 2024 00:50:09 -0700 (PDT) Message-ID: <770d3292-34cf-4e21-acb6-bd1f9caf5fef@suse.com> Date: Tue, 26 Mar 2024 08:50:07 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 5/5] x86/PVH: Support relocatable dom0 kernels Content-Language: en-US To: Jason Andryuk Cc: Andrew Cooper , =?UTF-8?Q?Roger_Pau_Monn=C3=A9?= , George Dunlap , Julien Grall , Stefano Stabellini , xen-devel@lists.xenproject.org References: <20240325204515.250203-1-jason.andryuk@amd.com> <20240325204515.250203-6-jason.andryuk@amd.com> From: Jan Beulich Autocrypt: addr=jbeulich@suse.com; keydata= xsDiBFk3nEQRBADAEaSw6zC/EJkiwGPXbWtPxl2xCdSoeepS07jW8UgcHNurfHvUzogEq5xk hu507c3BarVjyWCJOylMNR98Yd8VqD9UfmX0Hb8/BrA+Hl6/DB/eqGptrf4BSRwcZQM32aZK 7Pj2XbGWIUrZrd70x1eAP9QE3P79Y2oLrsCgbZJfEwCgvz9JjGmQqQkRiTVzlZVCJYcyGGsD /0tbFCzD2h20ahe8rC1gbb3K3qk+LpBtvjBu1RY9drYk0NymiGbJWZgab6t1jM7sk2vuf0Py O9Hf9XBmK0uE9IgMaiCpc32XV9oASz6UJebwkX+zF2jG5I1BfnO9g7KlotcA/v5ClMjgo6Gl MDY4HxoSRu3i1cqqSDtVlt+AOVBJBACrZcnHAUSuCXBPy0jOlBhxPqRWv6ND4c9PH1xjQ3NP nxJuMBS8rnNg22uyfAgmBKNLpLgAGVRMZGaGoJObGf72s6TeIqKJo/LtggAS9qAUiuKVnygo 3wjfkS9A3DRO+SpU7JqWdsveeIQyeyEJ/8PTowmSQLakF+3fote9ybzd880fSmFuIEJldWxp Y2ggPGpiZXVsaWNoQHN1c2UuY29tPsJgBBMRAgAgBQJZN5xEAhsDBgsJCAcDAgQVAggDBBYC AwECHgECF4AACgkQoDSui/t3IH4J+wCfQ5jHdEjCRHj23O/5ttg9r9OIruwAn3103WUITZee e7Sbg12UgcQ5lv7SzsFNBFk3nEQQCACCuTjCjFOUdi5Nm244F+78kLghRcin/awv+IrTcIWF hUpSs1Y91iQQ7KItirz5uwCPlwejSJDQJLIS+QtJHaXDXeV6NI0Uef1hP20+y8qydDiVkv6l IreXjTb7DvksRgJNvCkWtYnlS3mYvQ9NzS9PhyALWbXnH6sIJd2O9lKS1Mrfq+y0IXCP10eS FFGg+Av3IQeFatkJAyju0PPthyTqxSI4lZYuJVPknzgaeuJv/2NccrPvmeDg6Coe7ZIeQ8Yj t0ARxu2xytAkkLCel1Lz1WLmwLstV30g80nkgZf/wr+/BXJW/oIvRlonUkxv+IbBM3dX2OV8 AmRv1ySWPTP7AAMFB/9PQK/VtlNUJvg8GXj9ootzrteGfVZVVT4XBJkfwBcpC/XcPzldjv+3 HYudvpdNK3lLujXeA5fLOH+Z/G9WBc5pFVSMocI71I8bT8lIAzreg0WvkWg5V2WZsUMlnDL9 mpwIGFhlbM3gfDMs7MPMu8YQRFVdUvtSpaAs8OFfGQ0ia3LGZcjA6Ik2+xcqscEJzNH+qh8V m5jjp28yZgaqTaRbg3M/+MTbMpicpZuqF4rnB0AQD12/3BNWDR6bmh+EkYSMcEIpQmBM51qM EKYTQGybRCjpnKHGOxG0rfFY1085mBDZCH5Kx0cl0HVJuQKC+dV2ZY5AqjcKwAxpE75MLFkr wkkEGBECAAkFAlk3nEQCGwwACgkQoDSui/t3IH7nnwCfcJWUDUFKdCsBH/E5d+0ZnMQi+G0A nAuWpQkjM1ASeQwSHEeAWPgskBQL In-Reply-To: <20240325204515.250203-6-jason.andryuk@amd.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 25.03.2024 21:45, Jason Andryuk wrote: > +/* Find an e820 RAM region that fits the kernel at a suitable alignment. */ > +static paddr_t __init find_kernel_memory( > + const struct domain *d, struct elf_binary *elf, > + const struct elf_dom_parms *parms) > +{ > + paddr_t kernel_size = elf->dest_size; > + unsigned int i; > + > + for ( i = 0; i < d->arch.nr_e820; i++ ) > + { > + paddr_t start = d->arch.e820[i].addr; > + paddr_t end = start + d->arch.e820[i].size; > + paddr_t kstart, kend; > + > + if ( d->arch.e820[i].type != E820_RAM || > + d->arch.e820[i].size < kernel_size ) > + continue; > + > + kstart = ROUNDUP(start, parms->phys_align); > + kstart = max_t(paddr_t, kstart, parms->phys_min); > + kend = kstart + kernel_size; > + > + if ( kend - 1 > parms->phys_max ) > + return 0; > + > + if ( kend <= end ) > + return kstart; IOW within a suitable region the lowest suitable part is selected. Often low memory is deemed more precious than higher one, so if this choice is indeed intentional, I'd like to ask for a brief comment towards the reasons. > --- a/xen/common/libelf/libelf-dominfo.c > +++ b/xen/common/libelf/libelf-dominfo.c > @@ -17,6 +17,16 @@ > > #include "libelf-private.h" > > +#if defined(__i386__) || defined(__x86_64__) > +#define ARCH_PHYS_MIN_DEFAULT 0; > +#define ARCH_PHYS_MAX_DEFAULT (GB(4) - 1); > +#define ARCH_PHYS_ALIGN_DEFAULT MB(2); > +#else > +#define ARCH_PHYS_MIN_DEFAULT 0; > +#define ARCH_PHYS_MAX_DEFAULT 0; > +#define ARCH_PHYS_ALIGN_DEFAULT 0; > +#endif None of the semicolons should really be here. > @@ -227,6 +239,27 @@ elf_errorstatus elf_xen_parse_note(struct elf_binary *elf, > case XEN_ELFNOTE_PHYS32_ENTRY: > parms->phys_entry = val; > break; > + > + case XEN_ELFNOTE_PHYS32_RELOC: > + parms->phys_reloc = true; > + > + if ( descsz >= 4 ) > + { > + parms->phys_max = elf_note_numeric_array(elf, note, 4, 0); > + elf_msg(elf, " = max: %#"PRIx32, parms->phys_max); As indicated before, I consider the = here a little odd. > + } > + if ( descsz >= 8 ) > + { > + parms->phys_min = elf_note_numeric_array(elf, note, 4, 1); > + elf_msg(elf, " min: %#"PRIx32, parms->phys_min); > + } > + if ( descsz >= 12 ) > + { > + parms->phys_align = elf_note_numeric_array(elf, note, 4, 2); > + elf_msg(elf, " align: %#"PRIx32, parms->phys_align); > + } I'd like us to reconsider this ordering: I'm inclined to say that MAX isn't the most likely one a guest may find a need to use. Instead I'd expect both MIN and ALIGN wanting to be given higher priority; what I'm less certain about is the ordering between the two. To keep MIN and MAX adjacent, how about ALIGN, MIN, MAX? > --- a/xen/include/public/elfnote.h > +++ b/xen/include/public/elfnote.h > @@ -194,10 +194,27 @@ > */ > #define XEN_ELFNOTE_PHYS32_ENTRY 18 > > +/* > + * Physical loading constraints for PVH kernels > + * > + * The presence of this note indicates the kernel supports relocating itself. > + * > + * The note may include up to three 32bit values to place constraints on the > + * guest physical loading addresses and alignment for a PVH kernel. Values > + * are read in the following order: > + * - a maximum address for the entire image to be loaded below (default > + * 0xffffffff) "below" isn't exactly true anymore with this now being an inclusive value. Perhaps "up to", or perhaps more of a re-wording. I also think the wrapped line's indentation is too deep (by 2 blanks). > + * - a minimum address for the start of the image (default 0) > + * - a required start alignment (default 0x200000) > + * > + * This note is only valid for x86 binaries. Maybe s/valid/recognized/ (or honored or some such)? Jan